diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
new file mode 100644
index 00000000..1baaf6ca
--- /dev/null
+++ b/.github/workflows/coding-standards.yml
@@ -0,0 +1,66 @@
+name: "Coding Standards"
+
+on:
+  pull_request:
+    branches:
+      - "*.x"
+  push:
+    branches:
+      - "*.x"
+  schedule:
+    # Run workflow on every Sunday
+    - cron: '25 5 * * 0'
+
+jobs:
+  coding-standards:
+    name: "Coding Standards"
+    runs-on: "ubuntu-20.04"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.2"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+
+      - name: Setup cache environment
+        id: extcache
+        uses: shivammathur/cache-extensions@v1
+        with:
+          php-version: ${{ matrix.php-version }}
+          extensions: "mongodb"
+          key: "extcache-v1"
+
+      - name: Cache extensions
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.extcache.outputs.dir }}
+          key: ${{ steps.extcache.outputs.key }}
+          restore-keys: ${{ steps.extcache.outputs.key }}
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          extensions: "mongodb"
+          php-version: "${{ matrix.php-version }}"
+          tools: "cs2pr"
+
+      - name: "Show driver information"
+        run: "php --ri mongodb"
+
+      - name: "Cache dependencies installed with Composer"
+        uses: "actions/cache@v2"
+        with:
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-locked-${{ hashFiles('composer.json') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-normal-"
+
+      - name: "Install dependencies with Composer"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      # The -q option is required until phpcs v4 is released
+      - name: "Run PHP_CodeSniffer"
+        run: "vendor/bin/phpcs -q --no-colors --report=checkstyle | cs2pr"
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 00000000..cc9ef9f3
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,171 @@
+name: "Tests"
+
+on:
+  pull_request:
+    branches:
+      - "*.x"
+  push:
+    branches:
+      - "*.x"
+  schedule:
+    # Run workflow on every Sunday
+    - cron: '25 5 * * 0'
+
+jobs:
+  verification:
+    name: "Verification tests"
+    runs-on: "ubuntu-20.04"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+        with:
+          fetch-depth: 2
+
+      - name: Setup cache environment
+        id: extcache
+        uses: shivammathur/cache-extensions@v1
+        with:
+          php-version: "5.6"
+          extensions: "mongodb-1.7.5, mongo-1.6.14"
+          key: "extcache-v1"
+
+      - name: Cache extensions
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.extcache.outputs.dir }}
+          key: ${{ steps.extcache.outputs.key }}
+          restore-keys: ${{ steps.extcache.outputs.key }}
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          php-version: "5.6"
+          tools: "pecl"
+          extensions: "mongodb-1.7.5, mongo-1.6.14"
+          coverage: "none"
+          ini-values: "zend.assertions=1"
+
+      - name: "Show legacy driver information"
+        run: "php --ri mongo"
+
+      - name: "Show driver information"
+        run: "php --ri mongodb"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v2"
+        with:
+          path: "~/.composer/cache"
+          key: "php-5.6-composer-locked-${{ hashFiles('composer.json') }}"
+          restore-keys: "php-5.6-composer-normal-"
+
+      - name: "Install dependencies with composer"
+        run: "composer update --no-interaction --no-progress"
+
+      - id: setup-mongodb
+        uses: mongodb-labs/drivers-evergreen-tools@master
+        with:
+          version: "3.0"
+
+      - name: "Run PHPUnit"
+        run: "vendor/bin/simple-phpunit -v"
+        env:
+          SYMFONY_DEPRECATIONS_HELPER: 999999
+          MONGODB_URI: ${{ steps.setup-mongodb.outputs.cluster-uri }}
+
+  phpunit:
+    name: "PHPUnit tests"
+    runs-on: "${{ matrix.os }}"
+
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+          - "ubuntu-20.04"
+        php-version:
+          - "7.2"
+          - "7.3"
+          - "7.4"
+          - "8.0"
+          - "8.1"
+        mongodb-version:
+          - "4.4"
+        driver-version:
+          - "stable"
+        deps:
+          - "normal"
+        include:
+          - deps: "low"
+            os: "ubuntu-20.04"
+            php-version: "5.6"
+            mongodb-version: "3.0"
+            driver-version: "1.2.0"
+          - deps: "normal"
+            os: "ubuntu-20.04"
+            php-version: "7.0"
+            mongodb-version: "4.4"
+            driver-version: "1.9.2"
+          - deps: "normal"
+            os: "ubuntu-20.04"
+            php-version: "7.1"
+            mongodb-version: "4.4"
+            driver-version: "1.11.1"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2"
+        with:
+          fetch-depth: 2
+
+      - name: Setup cache environment
+        id: extcache
+        uses: shivammathur/cache-extensions@v1
+        with:
+          php-version: ${{ matrix.php-version }}
+          extensions: "mongodb-${{ matrix.driver-version }}"
+          key: "extcache-v1"
+
+      - name: Cache extensions
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.extcache.outputs.dir }}
+          key: ${{ steps.extcache.outputs.key }}
+          restore-keys: ${{ steps.extcache.outputs.key }}
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          php-version: "${{ matrix.php-version }}"
+          tools: "pecl"
+          extensions: "mongodb-${{ matrix.driver-version }}"
+          coverage: "none"
+          ini-values: "zend.assertions=1"
+
+      - name: "Show driver information"
+        run: "php --ri mongodb"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v2"
+        with:
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-locked-${{ hashFiles('composer.json') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.deps }}-"
+
+      - name: "Install dependencies with composer"
+        run: "composer update --no-interaction --no-progress"
+        if: "${{ matrix.deps == 'normal' }}"
+
+      - name: "Install lowest possible dependencies with composer"
+        run: "composer update --no-interaction --no-progress --prefer-dist --prefer-lowest"
+        if: "${{ matrix.deps == 'low' }}"
+
+      - id: setup-mongodb
+        uses: mongodb-labs/drivers-evergreen-tools@master
+        with:
+          version: ${{ matrix.mongodb-version }}
+
+      - name: "Run PHPUnit"
+        run: "vendor/bin/simple-phpunit -v"
+        env:
+          SYMFONY_DEPRECATIONS_HELPER: 999999
+          MONGODB_URI: ${{ steps.setup-mongodb.outputs.cluster-uri }}
diff --git a/.gitignore b/.gitignore
index 18389124..772a9a08 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
 composer.lock
+.phpcs-cache
+.phpunit.result.cache
 vendor/
 tests/scripts/
diff --git a/.scrutinizer.yml b/.scrutinizer.yml
deleted file mode 100644
index 47a7f6dd..00000000
--- a/.scrutinizer.yml
+++ /dev/null
@@ -1,6 +0,0 @@
-imports:
-    - php
-
-tools:
-    external_code_coverage:
-        timeout: 1200    # Timeout in seconds.
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 5123ec71..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,52 +0,0 @@
-dist: trusty
-sudo: false
-language: php
-
-services:
-  - mongodb
-
-php:
-  - 7.0
-  - 7.1
-  - 7.2
-
-env:
-  global:
-    - DRIVER_VERSION="stable"
-
-addons:
-  apt:
-    sources:
-      - sourceline: "deb [arch=amd64] https://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.4 multiverse"
-        key_url: "https://www.mongodb.org/static/pgp/server-3.4.asc"
-      - "mongodb-upstart"
-    packages: ['mongodb-org-server']
-
-matrix:
-  fast_finish: true
-  include:
-    # Test against legacy driver to ensure validity of the test suite
-    - php: 5.6
-      env: DRIVER_VERSION=stable LEGACY_DRIVER_VERSION=stable
-    # Test against set of lowest dependencies
-    - php: 5.6
-      env: DRIVER_VERSION="1.2.0" COMPOSER_FLAGS="--prefer-dist --prefer-lowest"
-      addons:
-        apt:
-          sources:
-            - sourceline: "deb [arch=amd64] https://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.0 multiverse"
-              key_url: "https://www.mongodb.org/static/pgp/server-3.0.asc"
-            - "mongodb-upstart"
-          packages: ['mongodb-org-server']
-
-before_install:
-  - pecl install -f mongodb-${DRIVER_VERSION}
-  - composer update ${COMPOSER_FLAGS}
-  - if [ "x$LEGACY_DRIVER_VERSION" != "x" ]; then yes '' | pecl -q install -f mongo-${LEGACY_DRIVER_VERSION}; fi
-
-script:
-  - ./vendor/bin/phpunit --coverage-clover=coverage.clover
-
-after_script:
-  - wget https://scrutinizer-ci.com/ocular.phar
-  - php ocular.phar code-coverage:upload --format=php-clover coverage.clover
diff --git a/CHANGELOG-1.1.md b/CHANGELOG-1.1.md
index 1aeae60f..f4b9e064 100644
--- a/CHANGELOG-1.1.md
+++ b/CHANGELOG-1.1.md
@@ -3,6 +3,98 @@ CHANGELOG for 1.1.x
 
 This changelog references the relevant changes done in minor version updates.
 
+1.1.11 (2019-11-11)
+-------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.11](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.11)
+milestone.
+
+ * [#263](https://github.com/alcaeus/mongo-php-adapter/pull/263) fixes test
+ failures on PHP 7.4.
+ * [#262](https://github.com/alcaeus/mongo-php-adapter/pull/262) fixes a memory
+ leak due to generators that aren't freed.
+
+1.1.10 (2019-11-06)
+-------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.10](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.10)
+milestone.
+
+ * [#261](https://github.com/alcaeus/mongo-php-adapter/pull/261) fixes missing
+ interface implementations in cursor classes.
+ * [#260](https://github.com/alcaeus/mongo-php-adapter/pull/260) fixes issues
+ when running against MongoDB 4.2 or `ext-mongodb` 1.6.
+ * [#259](https://github.com/alcaeus/mongo-php-adapter/pull/259) fixes issues on
+ PHP 7.3 due to `MongoCursor` not implementing `Countable`.
+
+1.1.9 (2019-08-07)
+------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.9](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.9)
+milestone.
+
+ * [#255](https://github.com/alcaeus/mongo-php-adapter/pull/255) fixes inserting
+ documents with identifiers PHP considers empty.
+
+1.1.8 (2019-07-14)
+------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.8](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.8)
+milestone.
+
+ * [#253](https://github.com/alcaeus/mongo-php-adapter/pull/253) fixes wrong
+ handling of `ArrayObject` instances in `MongoCollection::insert`.
+
+1.1.7 (2019-04-06)
+------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.7](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.7)
+milestone.
+
+ * [#250](https://github.com/alcaeus/mongo-php-adapter/pull/250) fixes type
+ conversion when passing write concern to `MongoClient` via URL arguments.
+
+
+1.1.6 (2019-02-08)
+------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.6](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.6)
+milestone.
+
+ * [#244](https://github.com/alcaeus/mongo-php-adapter/pull/244) fixes a null
+ access when converting exceptions.
+ * [#236](https://github.com/alcaeus/mongo-php-adapter/pull/236) allows using
+ `0` as key in documents.
+ * [#234](https://github.com/alcaeus/mongo-php-adapter/pull/234) removes an
+ invalid attribute from phpunit.xml.
+
+
+1.1.5 (2018-03-05)
+-----------------
+
+All issues and pull requests under this release may be found under the
+[1.1.5](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.5)
+milestone.
+
+ * [#222](https://github.com/alcaeus/mongo-php-adapter/pull/222) fixes handling
+ of `monodb+srv` URLs in `MongoClient`.
+
+1.1.4 (2018-01-24)
+------------------
+
+All issues and pull requests under this release may be found under the
+[1.1.4](https://github.com/alcaeus/mongo-php-adapter/issues?q=milestone%3A1.1.4)
+milestone.
+
+ * [#214](https://github.com/alcaeus/mongo-php-adapter/pull/214) fixes the
+return values of MongoBatch calls with unacknowledged write concerns.
+
 1.1.3 (2017-09-24)
 ------------------
 
diff --git a/README.md b/README.md
index 01df1f41..1cab6b7a 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ compatible with PHP 7.
 This library aims to provide a compatibility layer for applications that rely on
 libraries using ext-mongo, e.g.
 [Doctrine MongoDB ODM](https://github.com/doctrine/mongodb-odm), but want to
-migrate to PHP 7 or HHVM on which `ext-mongo` will not run.
+migrate to PHP 7 on which `ext-mongo` will not run.
 
 You should not be using this library if you do not rely on a library using
 `ext-mongo`. If you are starting a new project, please check out
diff --git a/composer.json b/composer.json
index aa2ce17a..dcc3041a 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,7 @@
 {
     "name": "alcaeus/mongo-php-adapter",
     "type": "library",
-    "description": "Adapter to provide ext-mongo interface on top of mongo-php-libary",
+    "description": "Adapter to provide ext-mongo interface on top of mongo-php-library",
     "keywords": ["mongodb", "database"],
     "license": "MIT",
     "authors": [
@@ -9,13 +9,15 @@
         { "name": "Olivier Lechevalier", "email": "olivier.lechevalier@gmail.com" }
     ],
     "require": {
-        "php": "^5.6 || ^7.0",
+        "php": "^5.6 || ^7.0 || ^8.0",
+        "ext-ctype": "*",
         "ext-hash": "*",
         "ext-mongodb": "^1.2.0",
         "mongodb/mongodb": "^1.0.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7 || ^6.0"
+        "symfony/phpunit-bridge": "^4.4.16 || ^5.2",
+        "squizlabs/php_codesniffer": "^3.2"
     },
     "provide": {
         "ext-mongo": "1.6.14"
@@ -33,8 +35,6 @@
         "psr-4": { "Alcaeus\\MongoDbAdapter\\Tests\\": "tests/Alcaeus/MongoDbAdapter" }
     },
     "extra": {
-        "branch-alias": {
-            "dev-master": "1.1.x-dev"
-        }
+        "branch-version": "1.x"
     }
 }
diff --git a/lib/Alcaeus/MongoDbAdapter/AbstractCursor.php b/lib/Alcaeus/MongoDbAdapter/AbstractCursor.php
index 6e3c8758..f1d76ebb 100644
--- a/lib/Alcaeus/MongoDbAdapter/AbstractCursor.php
+++ b/lib/Alcaeus/MongoDbAdapter/AbstractCursor.php
@@ -18,6 +18,7 @@
 use Alcaeus\MongoDbAdapter\Helper\ReadPreference;
 use MongoDB\Collection;
 use MongoDB\Driver\Cursor;
+use ReturnTypeWillChange;
 
 /**
  * @internal
@@ -52,7 +53,7 @@ abstract class AbstractCursor
     protected $db;
 
     /**
-     * @var \Iterator
+     * @var CursorIterator
      */
     protected $iterator;
 
@@ -136,6 +137,7 @@ public function __construct(\MongoClient $connection, $ns)
      * @link http://www.php.net/manual/en/mongocursor.current.php
      * @return array
      */
+    #[ReturnTypeWillChange]
     public function current()
     {
         return $this->current;
@@ -146,6 +148,7 @@ public function current()
      * @link http://www.php.net/manual/en/mongocursor.key.php
      * @return string The current result's _id as a string.
      */
+    #[ReturnTypeWillChange]
     public function key()
     {
         return $this->key;
@@ -158,6 +161,7 @@ public function key()
      * @throws \MongoCursorTimeoutException
      * @return array Returns the next object
      */
+    #[ReturnTypeWillChange]
     public function next()
     {
         if (! $this->startedIterating) {
@@ -181,6 +185,7 @@ public function next()
      * @throws \MongoCursorTimeoutException
      * @return void
      */
+    #[ReturnTypeWillChange]
     public function rewind()
     {
         // We can recreate the cursor to allow it to be rewound
@@ -196,6 +201,7 @@ public function rewind()
      * @link http://www.php.net/manual/en/mongocursor.valid.php
      * @return boolean If the current result is not null.
      */
+    #[ReturnTypeWillChange]
     public function valid()
     {
         return $this->valid;
@@ -292,9 +298,8 @@ protected function getOptions($optionNames = null)
     protected function ensureIterator()
     {
         if ($this->iterator === null) {
-            // MongoDB\Driver\Cursor needs to be wrapped into a \Generator so that a valid \Iterator with working implementations of
-            // next, current, valid, key and rewind is returned. These methods don't work if we wrap the Cursor inside an \IteratorIterator
             $this->iterator = $this->wrapTraversable($this->ensureCursor());
+            $this->iterator->rewind();
         }
 
         return $this->iterator;
@@ -302,13 +307,11 @@ protected function ensureIterator()
 
     /**
      * @param \Traversable $traversable
-     * @return \Generator
+     * @return CursorIterator
      */
     protected function wrapTraversable(\Traversable $traversable)
     {
-        foreach ($traversable as $key => $value) {
-            yield $key => $value;
-        }
+        return new CursorIterator($traversable);
     }
 
     /**
diff --git a/lib/Alcaeus/MongoDbAdapter/CursorIterator.php b/lib/Alcaeus/MongoDbAdapter/CursorIterator.php
new file mode 100644
index 00000000..31057584
--- /dev/null
+++ b/lib/Alcaeus/MongoDbAdapter/CursorIterator.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Alcaeus\MongoDbAdapter;
+
+use IteratorIterator;
+use MongoDB\BSON\ObjectID;
+use Traversable;
+use ReturnTypeWillChange;
+
+/**
+ * @internal
+ */
+final class CursorIterator extends IteratorIterator
+{
+    /** @var bool */
+    private $useIdAsKey;
+
+    public function __construct(Traversable $iterator, $useIdAsKey = false)
+    {
+        parent::__construct($iterator);
+
+        $this->useIdAsKey = $useIdAsKey;
+    }
+
+    #[ReturnTypeWillChange]
+    public function key()
+    {
+        if (!$this->useIdAsKey) {
+            return parent::key();
+        }
+
+        $current = $this->current();
+
+        if (!isset($current->_id) || (is_object($current->_id) && !$current->_id instanceof ObjectID)) {
+            return parent::key();
+        }
+
+        return (string) $current->_id;
+    }
+}
diff --git a/lib/Alcaeus/MongoDbAdapter/ExceptionConverter.php b/lib/Alcaeus/MongoDbAdapter/ExceptionConverter.php
index 8838a698..9bc442ae 100644
--- a/lib/Alcaeus/MongoDbAdapter/ExceptionConverter.php
+++ b/lib/Alcaeus/MongoDbAdapter/ExceptionConverter.php
@@ -16,6 +16,8 @@
 namespace Alcaeus\MongoDbAdapter;
 
 use MongoDB\Driver\Exception;
+use MongoDB\Driver\WriteError;
+use MongoDB\Driver\WriteResult;
 
 /**
  * @internal
@@ -30,6 +32,12 @@ class ExceptionConverter
      */
     public static function toLegacy(Exception\Exception $e, $fallbackClass = 'MongoException')
     {
+        // Starting with ext-mongodb 1.6.0, errors during bulk write are always wrapped in a BulkWriteException.
+        // If a BulkWriteException wraps another driver exception, use that instead.
+        if ($e instanceof Exception\BulkWriteException && $e->getPrevious() instanceof Exception\Exception) {
+            $e = $e->getPrevious();
+        }
+
         $message = $e->getMessage();
         $code = $e->getCode();
 
@@ -44,12 +52,13 @@ public static function toLegacy(Exception\Exception $e, $fallbackClass = 'MongoE
             case Exception\BulkWriteException::class:
             case Exception\WriteException::class:
                 $writeResult = $e->getWriteResult();
-
-                if ($writeResult) {
+                // attempt to retrieve write error
+                if ($writeResult instanceof WriteResult && is_array($writeResult->getWriteErrors()) && $writeResult->getWriteErrors() !== []) {
                     $writeError = $writeResult->getWriteErrors()[0];
-
-                    $message = $writeError->getMessage();
-                    $code = $writeError->getCode();
+                    if ($writeError instanceof WriteError) {
+                        $message = $writeError->getMessage();
+                        $code = $writeError->getCode();
+                    }
                 }
 
                 switch ($code) {
diff --git a/lib/Alcaeus/MongoDbAdapter/TypeConverter.php b/lib/Alcaeus/MongoDbAdapter/TypeConverter.php
index ad10ba75..51ad7c6c 100644
--- a/lib/Alcaeus/MongoDbAdapter/TypeConverter.php
+++ b/lib/Alcaeus/MongoDbAdapter/TypeConverter.php
@@ -43,6 +43,8 @@ public static function fromLegacy($value)
                 return $value->toBSONType();
             case $value instanceof BSON\Type:
                 return $value;
+            case $value instanceof \DateTimeInterface:
+                return self::fromLegacy((array) $value);
             case is_array($value):
             case is_object($value):
                 $result = [];
@@ -176,7 +178,7 @@ private static function convertBSONObjectToLegacy(BSON\Type $value)
             case $value instanceof Model\BSONDocument:
             case $value instanceof Model\BSONArray:
                 return array_map(
-                    ['self', 'toLegacy'],
+                    [self::class, 'toLegacy'],
                     $value->getArrayCopy()
                 );
             default:
diff --git a/lib/Alcaeus/MongoDbAdapter/TypeInterface.php b/lib/Alcaeus/MongoDbAdapter/TypeInterface.php
index 3f079830..2126e161 100644
--- a/lib/Alcaeus/MongoDbAdapter/TypeInterface.php
+++ b/lib/Alcaeus/MongoDbAdapter/TypeInterface.php
@@ -15,8 +15,6 @@
 
 namespace Alcaeus\MongoDbAdapter;
 
-use MongoDB\BSON\Type;
-
 interface TypeInterface
 {
     /**
diff --git a/lib/Mongo/MongoClient.php b/lib/Mongo/MongoClient.php
index 0e0fae57..a88f10e6 100644
--- a/lib/Mongo/MongoClient.php
+++ b/lib/Mongo/MongoClient.php
@@ -32,13 +32,13 @@ class MongoClient
     use Helper\WriteConcern;
 
     const VERSION = '1.6.12';
-    const DEFAULT_HOST = "localhost" ;
-    const DEFAULT_PORT = 27017 ;
-    const RP_PRIMARY = "primary" ;
-    const RP_PRIMARY_PREFERRED = "primaryPreferred" ;
-    const RP_SECONDARY = "secondary" ;
-    const RP_SECONDARY_PREFERRED = "secondaryPreferred" ;
-    const RP_NEAREST = "nearest" ;
+    const DEFAULT_HOST = "localhost";
+    const DEFAULT_PORT = 27017;
+    const RP_PRIMARY = "primary";
+    const RP_PRIMARY_PREFERRED = "primaryPreferred";
+    const RP_SECONDARY = "secondary";
+    const RP_SECONDARY_PREFERRED = "secondaryPreferred";
+    const RP_NEAREST = "nearest";
 
     /**
      * @var bool
@@ -93,10 +93,10 @@ public function __construct($server = 'default', array $options = ['connect' =>
         $this->applyConnectionOptions($server, $options);
 
         $this->server = $server;
-        if (false === strpos($this->server, 'mongodb://')) {
-            $this->server = 'mongodb://'.$this->server;
+        if (false === strpos($this->server, '://')) {
+            $this->server = 'mongodb://' . $this->server;
         }
-        $this->client = new Client($this->server, $options, $driverOptions);
+        $this->client = new Client($this->server, $options, $driverOptions + ['driver' => ['name' => 'mongo-php-adapter']]);
         $info = $this->client->__debugInfo();
         $this->manager = $info['manager'];
 
@@ -222,7 +222,7 @@ public function getHosts()
             $results[$key] = [
                 'host' => $server->getHost(),
                 'port' => $server->getPort(),
-                'health' => (int) $info['ok'],
+                'health' => 1,
                 'state' => $state,
                 'ping' => $server->getLatency(),
                 'lastPing' => null,
@@ -352,7 +352,7 @@ private function notImplemented()
     /**
      * @return array
      */
-    function __sleep()
+    public function __sleep()
     {
         return [
             'connected', 'status', 'server', 'persistent'
@@ -365,7 +365,12 @@ function __sleep()
      */
     private function extractUrlOptions($server)
     {
-        $queryOptions = explode('&', parse_url($server, PHP_URL_QUERY));
+        $queryOptions = parse_url($server, PHP_URL_QUERY);
+        if (!$queryOptions) {
+            return [];
+        }
+
+        $queryOptions = explode('&', $queryOptions);
 
         $options = [];
         foreach ($queryOptions as $option) {
@@ -376,6 +381,8 @@ private function extractUrlOptions($server)
             $keyValue = explode('=', $option);
             if ($keyValue[0] === 'readPreferenceTags') {
                 $options[$keyValue[0]][] = $this->getReadPreferenceTags($keyValue[1]);
+            } elseif (ctype_digit($keyValue[1])) {
+                $options[$keyValue[0]] = (int) $keyValue[1];
             } else {
                 $options[$keyValue[0]] = $keyValue[1];
             }
diff --git a/lib/Mongo/MongoCode.php b/lib/Mongo/MongoCode.php
index 25d6b5f0..dd792f80 100644
--- a/lib/Mongo/MongoCode.php
+++ b/lib/Mongo/MongoCode.php
@@ -27,7 +27,7 @@ class MongoCode implements \Alcaeus\MongoDbAdapter\TypeInterface
     private $code;
 
     /**
-     * @var array
+     * @var array|null
      */
     private $scope;
 
@@ -65,6 +65,6 @@ public function __toString()
      */
     public function toBSONType()
     {
-        return new \MongoDB\BSON\Javascript($this->code, $this->scope);
+        return new \MongoDB\BSON\Javascript($this->code, !empty($this->scope) ? $this->scope : null);
     }
 }
diff --git a/lib/Mongo/MongoCollection.php b/lib/Mongo/MongoCollection.php
index 64070b70..aa858200 100644
--- a/lib/Mongo/MongoCollection.php
+++ b/lib/Mongo/MongoCollection.php
@@ -20,6 +20,8 @@
 use Alcaeus\MongoDbAdapter\Helper;
 use Alcaeus\MongoDbAdapter\TypeConverter;
 use Alcaeus\MongoDbAdapter\ExceptionConverter;
+use MongoDB\Driver\Exception\CommandException;
+use MongoDB\Model\IndexInput;
 
 /**
  * Represents a database collection.
@@ -277,7 +279,7 @@ public function validate($scan_data = false)
      */
     public function insert(&$a, array $options = [])
     {
-        if (! $this->ensureDocumentHasMongoId($a)) {
+        if ($this->ensureDocumentHasMongoId($a) === null) {
             trigger_error(sprintf('%s(): expects parameter %d to be an array or object, %s given', __METHOD__, 1, gettype($a)), E_USER_WARNING);
             return;
         }
@@ -596,7 +598,7 @@ public function createIndex($keys, array $options = [])
         }
 
         if (! isset($options['name'])) {
-            $options['name'] = \MongoDB\generate_index_name($keys);
+            $options['name'] = $this->generateIndexName($keys);
         }
 
         $indexes = iterator_to_array($this->collection->listIndexes());
@@ -626,7 +628,9 @@ public function createIndex($keys, array $options = [])
 
             $this->collection->createIndex($keys, $options);
         } catch (\MongoDB\Driver\Exception\Exception $e) {
-            throw ExceptionConverter::toLegacy($e, 'MongoResultException');
+            if (! $e instanceof CommandException || strpos($e->getMessage(), 'with a different name') === false) {
+                throw ExceptionConverter::toLegacy($e, 'MongoResultException');
+            }
         }
 
         $result = [
@@ -674,7 +678,7 @@ public function deleteIndex($keys)
                 $indexName .= '_1';
             }
         } elseif (is_array($keys)) {
-            $indexName = \MongoDB\generate_index_name($keys);
+            $indexName = $this->generateIndexName($keys);
         } else {
             throw new \InvalidArgumentException();
         }
@@ -888,14 +892,14 @@ public function group($keys, array $initial, $reduce, array $condition = [])
         $command = [
             'group' => [
                 'ns' => $this->name,
-                '$reduce' => (string)$reduce,
+                '$reduce' => (string) $reduce,
                 'initial' => $initial,
                 'cond' => $condition,
             ],
         ];
 
         if ($keys instanceof MongoCode) {
-            $command['group']['$keyf'] = (string)$keys;
+            $command['group']['$keyf'] = (string) $keys;
         } else {
             $command['group']['key'] = $keys;
         }
@@ -904,7 +908,7 @@ public function group($keys, array $initial, $reduce, array $condition = [])
         }
         if (array_key_exists('finalize', $condition)) {
             if ($condition['finalize'] instanceof MongoCode) {
-                $condition['finalize'] = (string)$condition['finalize'];
+                $condition['finalize'] = (string) $condition['finalize'];
             }
             $command['group']['finalize'] = $condition['finalize'];
         }
@@ -983,7 +987,7 @@ private function convertWriteConcernOptions(array $options)
     private function checkKeys(array $array)
     {
         foreach ($array as $key => $value) {
-            if (empty($key) && $key !== 0) {
+            if (empty($key) && $key !== 0 && $key !== '0') {
                 throw new \MongoException('zero-length keys are not allowed, did you use $ with double quotes?');
             }
 
@@ -999,12 +1003,12 @@ private function checkKeys(array $array)
      */
     private function ensureDocumentHasMongoId(&$document)
     {
-        if (is_array($document)) {
+        if (is_array($document) || $document instanceof ArrayObject) {
             if (! isset($document['_id'])) {
                 $document['_id'] = new \MongoId();
             }
 
-            $this->checkKeys($document);
+            $this->checkKeys((array) $document);
 
             return $document['_id'];
         } elseif (is_object($document)) {
@@ -1036,6 +1040,22 @@ private function checkCollectionName($name)
         }
     }
 
+
+    /**
+     * @param array $keys Field or fields to use as index.
+     * @return string
+     */
+    private function generateIndexName($keys)
+    {
+        $name = '';
+
+        foreach ($keys as $field => $type) {
+            $name .= ($name !== '' ? '_' : '') . $field . '_' . $type;
+        }
+
+        return $name;
+    }
+
     /**
      * @return array
      */
diff --git a/lib/Mongo/MongoCursor.php b/lib/Mongo/MongoCursor.php
index e98a2671..07be69aa 100644
--- a/lib/Mongo/MongoCursor.php
+++ b/lib/Mongo/MongoCursor.php
@@ -18,17 +18,17 @@
 }
 
 use Alcaeus\MongoDbAdapter\AbstractCursor;
+use Alcaeus\MongoDbAdapter\CursorIterator;
 use Alcaeus\MongoDbAdapter\TypeConverter;
 use Alcaeus\MongoDbAdapter\ExceptionConverter;
 use MongoDB\Driver\Cursor;
-use MongoDB\Driver\ReadPreference;
 use MongoDB\Operation\Find;
 
 /**
  * Result object for database query.
  * @link http://www.php.net/manual/en/class.mongocursor.php
  */
-class MongoCursor extends AbstractCursor implements Iterator
+class MongoCursor extends AbstractCursor implements Iterator, Countable, MongoCursorInterface
 {
     /**
      * @var bool
@@ -133,6 +133,7 @@ public function awaitData($wait = true)
      * @param bool $foundOnly Send cursor limit and skip information to the count function, if applicable.
      * @return int The number of documents returned by this cursor's query.
      */
+    #[\ReturnTypeWillChange]
     public function count($foundOnly = false)
     {
         $optionNames = ['hint', 'maxTimeMS'];
@@ -472,16 +473,11 @@ protected function ensureCursor()
 
     /**
      * @param \Traversable $traversable
-     * @return \Generator
+     * @return CursorIterator
      */
     protected function wrapTraversable(\Traversable $traversable)
     {
-        foreach ($traversable as $key => $value) {
-            if (isset($value->_id) && ($value->_id instanceof \MongoDB\BSON\ObjectID || !is_object($value->_id))) {
-                $key = (string) $value->_id;
-            }
-            yield $key => $value;
-        }
+        return new CursorIterator($traversable, true);
     }
 
     /**
diff --git a/lib/Mongo/MongoDB.php b/lib/Mongo/MongoDB.php
index 61750db3..f9a0f112 100644
--- a/lib/Mongo/MongoDB.php
+++ b/lib/Mongo/MongoDB.php
@@ -154,7 +154,9 @@ public function getCollectionInfo(array $options = [])
                     'info' => isset($info['info']) ? (array) $info['info'] : null,
                     'idIndex' => isset($info['idIndex']) ? (array) $info['idIndex'] : null,
                 ],
-                function ($item) { return $item !== null; }
+                function ($item) {
+                    return $item !== null;
+                }
             );
         };
 
diff --git a/lib/Mongo/MongoDate.php b/lib/Mongo/MongoDate.php
index 6c1e657a..7571ca84 100644
--- a/lib/Mongo/MongoDate.php
+++ b/lib/Mongo/MongoDate.php
@@ -88,15 +88,14 @@ public function toBSONType()
     public function toDateTime()
     {
         $datetime = new \DateTime();
+        $datetime->setTimezone(new \DateTimeZone("UTC"));
         $datetime->setTimestamp($this->sec);
 
         $microSeconds = $this->truncateMicroSeconds($this->usec);
         if ($microSeconds > 0) {
-            $datetime = \DateTime::createFromFormat('Y-m-d H:i:s.u', $datetime->format('Y-m-d H:i:s') . '.' . str_pad($microSeconds, 6, '0', STR_PAD_LEFT));
+            $datetime = \DateTime::createFromFormat('Y-m-d H:i:s.u e', $datetime->format('Y-m-d H:i:s') . '.' . str_pad($microSeconds, 6, '0', STR_PAD_LEFT) . ' UTC');
         }
 
-        $datetime->setTimezone(new \DateTimeZone("UTC"));
-
         return $datetime;
     }
 
diff --git a/lib/Mongo/MongoGridFS.php b/lib/Mongo/MongoGridFS.php
index 56718d3d..7105fbaa 100644
--- a/lib/Mongo/MongoGridFS.php
+++ b/lib/Mongo/MongoGridFS.php
@@ -207,7 +207,7 @@ public function storeBytes($bytes, array $extra = [], array $options = [])
         try {
             $file = $this->insertFile($record, $options);
         } catch (MongoException $e) {
-            throw new MongoGridFSException('Could not store file: '. $e->getMessage(), $e->getCode(), $e);
+            throw new MongoGridFSException('Could not store file: ' . $e->getMessage(), $e->getCode(), $e);
         }
 
         try {
diff --git a/lib/Mongo/MongoGridFSCursor.php b/lib/Mongo/MongoGridFSCursor.php
index bec7b444..3da1542a 100644
--- a/lib/Mongo/MongoGridFSCursor.php
+++ b/lib/Mongo/MongoGridFSCursor.php
@@ -17,7 +17,7 @@
     return;
 }
 
-class MongoGridFSCursor extends MongoCursor
+class MongoGridFSCursor extends MongoCursor implements Countable
 {
     /**
      * @static
@@ -68,6 +68,6 @@ public function current()
     public function key()
     {
         $file = $this->current();
-        return ($file !== null) ? (string)$file->file['_id'] : null;
+        return ($file !== null) ? (string) $file->file['_id'] : null;
     }
 }
diff --git a/lib/Mongo/MongoId.php b/lib/Mongo/MongoId.php
index a83b98eb..7a665b41 100644
--- a/lib/Mongo/MongoId.php
+++ b/lib/Mongo/MongoId.php
@@ -202,6 +202,7 @@ public static function __set_state(array $props)
     /**
      * @return stdClass
      */
+    #[ReturnTypeWillChange]
     public function jsonSerialize()
     {
         $object = new stdClass();
diff --git a/lib/Mongo/MongoWriteBatch.php b/lib/Mongo/MongoWriteBatch.php
index 399cc965..991f2450 100644
--- a/lib/Mongo/MongoWriteBatch.php
+++ b/lib/Mongo/MongoWriteBatch.php
@@ -83,7 +83,7 @@ protected function __construct(MongoCollection $collection, $batchType, $writeOp
     public function add($item)
     {
         if (is_object($item)) {
-            $item = (array)$item;
+            $item = (array) $item;
         }
 
         $this->validate($item);
@@ -132,6 +132,17 @@ final public function execute(array $writeOptions = [])
 
         switch ($this->batchType) {
             case self::COMMAND_UPDATE:
+                if ($options['writeConcern']->getW() === 0) {
+                    $resultDocument += [
+                        'nMatched' => 0,
+                        'nModified' => 0,
+                        'nUpserted' => 0,
+                        'ok' => true,
+                    ];
+
+                    break;
+                }
+
                 $upsertedIds = [];
                 foreach ($writeResult->getUpsertedIds() as $index => $id) {
                     $upsertedIds[] = [
@@ -153,6 +164,15 @@ final public function execute(array $writeOptions = [])
                 break;
 
             case self::COMMAND_DELETE:
+                if ($options['writeConcern']->getW() === 0) {
+                    $resultDocument += [
+                        'nRemoved' => 0,
+                        'ok' => true,
+                    ];
+
+                    break;
+                }
+
                 $resultDocument += [
                     'nRemoved' => $writeResult->getDeletedCount(),
                     'ok' => true,
@@ -160,6 +180,15 @@ final public function execute(array $writeOptions = [])
                 break;
 
             case self::COMMAND_INSERT:
+                if ($options['writeConcern']->getW() === 0) {
+                    $resultDocument += [
+                        'nInserted' => 0,
+                        'ok' => true,
+                    ];
+
+                    break;
+                }
+
                 $resultDocument += [
                     'nInserted' => $writeResult->getInsertedCount(),
                     'ok' => true,
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
new file mode 100644
index 00000000..ca441e66
--- /dev/null
+++ b/phpcs.xml.dist
@@ -0,0 +1,45 @@
+<?xml version="1.0"?>
+<ruleset>
+    <arg name="basepath" value="."/>
+    <arg name="extensions" value="php"/>
+    <arg name="parallel" value="80"/>
+    <arg name="cache" value=".phpcs-cache"/>
+    <arg name="colors" />
+
+    <!-- Ignore warnings and show progress of the run -->
+    <arg value="np"/>
+
+    <file>lib</file>
+    <file>tests</file>
+
+    <rule ref="PSR1.Classes.ClassDeclaration.MultipleClasses">
+        <exclude-pattern>*/tests/*</exclude-pattern>
+    </rule>
+
+    <!-- Import PSR-2 coding standard (base) -->
+    <rule ref="PSR2">
+        <!-- Using \Doctrine\Sniffs\Spacing\ControlStructureSniff instead -->
+        <exclude name="PSR2.ControlStructures.ControlStructureSpacing"/>
+    </rule>
+
+    <!-- Import PSR-2 coding standard (base) -->
+    <rule ref="PSR1.Classes.ClassDeclaration.MissingNamespace">
+        <exclude-pattern>*/lib/Mongo/*</exclude-pattern>
+    </rule>
+
+    <!-- Disallow else if in favour elseif -->
+    <rule ref="PSR2.ControlStructures.ElseIfDeclaration.NotAllowed">
+        <type>error</type>
+    </rule>
+
+    <!-- Force whitespace after a type cast -->
+    <rule ref="Generic.Formatting.SpaceAfterCast" />
+
+    <!-- Force whitespace before and after concatenation -->
+    <rule ref="Squiz.Strings.ConcatenationSpacing">
+        <properties>
+            <property name="spacing" value="1"/>
+            <property name="ignoreNewlines" value="true"/>
+        </properties>
+    </rule>
+</ruleset>
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 3a237d32..eaa58e59 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -7,12 +7,13 @@
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          stopOnFailure="false"
-         syntaxCheck="false"
+         bootstrap="vendor/autoload.php"
 >
     <php>
         <!-- Disable deprecation warnings -->
         <!-- php -r 'echo -1 & ~E_USER_DEPRECATED & ~E_DEPRECATED;' -->
         <ini name="error_reporting" value="-24577"/>
+        <const name="MONGODB_URI" value="mongodb://localhost:27017" />
     </php>
 
     <testsuites>
@@ -20,10 +21,4 @@
             <directory>./tests/Alcaeus/MongoDbAdapter/</directory>
         </testsuite>
     </testsuites>
-
-    <filter>
-        <whitelist>
-            <directory suffix=".php">./lib/Alcaeus/MongoDbAdapter</directory>
-        </whitelist>
-    </filter>
 </phpunit>
diff --git a/tests/Alcaeus/MongoDbAdapter/Constraint/Constraint.php b/tests/Alcaeus/MongoDbAdapter/Constraint/Constraint.php
new file mode 100644
index 00000000..8a908f1c
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/Constraint/Constraint.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Alcaeus\MongoDbAdapter\Tests\Constraint;
+
+use PHPUnit\Framework\Constraint\Constraint as BaseConstraint;
+use function class_exists;
+
+if (class_exists('PHPUnit_Framework_Constraint')) {
+    abstract class Constraint extends \PHPUnit_Framework_Constraint
+    {
+    }
+} else {
+    abstract class Constraint extends BaseConstraint
+    {
+    }
+}
diff --git a/tests/Alcaeus/MongoDbAdapter/Constraint/ConstraintTrait.php b/tests/Alcaeus/MongoDbAdapter/Constraint/ConstraintTrait.php
new file mode 100644
index 00000000..3934a7b8
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/Constraint/ConstraintTrait.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Alcaeus\MongoDbAdapter\Tests\Constraint;
+
+use Symfony\Bridge\PhpUnit\ConstraintTrait as BaseConstraintTrait;
+use Symfony\Bridge\PhpUnit\Legacy\ConstraintTraitForV6;
+
+if (class_exists('PHPUnit_Framework_Constraint')) {
+    trait ConstraintTrait
+    {
+        use ConstraintTraitForV6;
+    }
+} else {
+    trait ConstraintTrait
+    {
+        use BaseConstraintTrait;
+    }
+}
diff --git a/tests/Alcaeus/MongoDbAdapter/Constraint/LICENSE b/tests/Alcaeus/MongoDbAdapter/Constraint/LICENSE
new file mode 100644
index 00000000..d6456956
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/Constraint/LICENSE
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
diff --git a/tests/Alcaeus/MongoDbAdapter/Constraint/Matches.php b/tests/Alcaeus/MongoDbAdapter/Constraint/Matches.php
new file mode 100644
index 00000000..fa1b1620
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/Constraint/Matches.php
@@ -0,0 +1,386 @@
+<?php
+
+namespace Alcaeus\MongoDbAdapter\Tests\Constraint;
+
+use LogicException;
+use MongoDB\BSON\Int64;
+use MongoDB\BSON\Serializable;
+use MongoDB\BSON\Type;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
+use PHPUnit\Framework\Assert;
+use PHPUnit\Framework\ExpectationFailedException;
+use RuntimeException;
+use SebastianBergmann\Comparator\ComparisonFailure;
+use SebastianBergmann\Comparator\Factory;
+use function array_keys;
+use function count;
+use function get_class;
+use function gettype;
+use function is_array;
+use function is_float;
+use function is_int;
+use function is_object;
+use function range;
+use function sprintf;
+use function strpos;
+use const PHP_INT_SIZE;
+
+/**
+ * Constraint that checks if one value matches another.
+ *
+ * The expected value is passed in the constructor. Behavior for allowing extra
+ * keys in root documents and processing operators is also configurable.
+ */
+class Matches extends Constraint
+{
+    use ConstraintTrait;
+
+    /** @var mixed */
+    private $value;
+
+    /** @var bool */
+    private $allowExtraRootKeys;
+
+    /** @var bool */
+    private $allowExtraKeys;
+
+    /** @var bool */
+    private $allowOperators;
+
+    /** @var ComparisonFailure|null */
+    private $lastFailure;
+
+    public function __construct($value, $allowExtraRootKeys = true, $allowExtraKeys = false, $allowOperators = true)
+    {
+        $this->value = self::prepare($value);
+        $this->allowExtraRootKeys = $allowExtraRootKeys;
+        $this->allowExtraKeys = $allowExtraKeys;
+        $this->allowOperators = $allowOperators;
+        $this->comparatorFactory = Factory::getInstance();
+    }
+
+    private function doEvaluate($other, $description = '', $returnResult = false)
+    {
+        $other = self::prepare($other);
+        $success = false;
+        $this->lastFailure = null;
+
+        try {
+            $this->assertMatches($this->value, $other);
+            $success = true;
+        } catch (ExpectationFailedException $e) {
+            /* Rethrow internal assertion failures (e.g. operator type checks,
+             * EntityMap errors), which are logical errors in the code/test. */
+            throw $e;
+        } catch (RuntimeException $e) {
+            /* This will generally catch internal errors from failAt(), which
+             * include a key path to pinpoint the failure. */
+            $this->lastFailure = new ComparisonFailure(
+                $this->value,
+                $other,
+                /* TODO: Improve the exporter to canonicalize documents by
+                 * sorting keys and remove spl_object_hash from output. */
+                $this->exporter()->export($this->value),
+                $this->exporter()->export($other),
+                false,
+                $e->getMessage()
+            );
+        }
+
+        if ($returnResult) {
+            return $success;
+        }
+
+        if (! $success) {
+            $this->fail($other, $description, $this->lastFailure);
+        }
+    }
+
+    private function assertEquals($expected, $actual, $keyPath)
+    {
+        $expectedType = is_object($expected) ? get_class($expected) : gettype($expected);
+        $actualType = is_object($actual) ? get_class($actual) : gettype($actual);
+
+        /* Early check to work around ObjectComparator printing the entire value
+         * for a failed type comparison. Avoid doing this if either value is
+         * numeric to allow for flexible numeric comparisons (e.g. 1 == 1.0). */
+        if ($expectedType !== $actualType && ! (self::isNumeric($expected) || self::isNumeric($actual))) {
+            self::failAt(sprintf('%s is not expected type "%s"', $actualType, $expectedType), $keyPath);
+        }
+
+        try {
+            $this->comparatorFactory->getComparatorFor($expected, $actual)->assertEquals($expected, $actual);
+        } catch (ComparisonFailure $e) {
+            /* Disregard other ComparisonFailure fields, as evaluate() only uses
+             * the message when creating its own ComparisonFailure. */
+            self::failAt($e->getMessage(), $keyPath);
+        }
+    }
+
+    private function assertMatches($expected, $actual, $keyPath = '')
+    {
+        if ($expected instanceof BSONArray) {
+            $this->assertMatchesArray($expected, $actual, $keyPath);
+
+            return;
+        }
+
+        if ($expected instanceof BSONDocument) {
+            $this->assertMatchesDocument($expected, $actual, $keyPath);
+
+            return;
+        }
+
+        $this->assertEquals($expected, $actual, $keyPath);
+    }
+
+    private function assertMatchesArray(BSONArray $expected, $actual, $keyPath)
+    {
+        if (! $actual instanceof BSONArray) {
+            $actualType = is_object($actual) ? get_class($actual) : gettype($actual);
+            self::failAt(sprintf('%s is not instance of expected class "%s"', $actualType, BSONArray::class), $keyPath);
+        }
+
+        if (count($expected) !== count($actual)) {
+            self::failAt(sprintf('$actual count is %d, expected %d', count($actual), count($expected)), $keyPath);
+        }
+
+        foreach ($expected as $key => $expectedValue) {
+            $this->assertMatches(
+                $expectedValue,
+                $actual[$key],
+                (empty($keyPath) ? $key : $keyPath . '.' . $key)
+            );
+        }
+    }
+
+    private function assertMatchesDocument(BSONDocument $expected, $actual, $keyPath)
+    {
+        if ($this->allowOperators && self::isOperator($expected)) {
+            $this->assertMatchesOperator($expected, $actual, $keyPath);
+
+            return;
+        }
+
+        if (! $actual instanceof BSONDocument) {
+            $actualType = is_object($actual) ? get_class($actual) : gettype($actual);
+            self::failAt(sprintf('%s is not instance of expected class "%s"', $actualType, BSONDocument::class), $keyPath);
+        }
+
+        foreach ($expected as $key => $expectedValue) {
+            $actualKeyExists = $actual->offsetExists($key);
+
+            if ($this->allowOperators && $expectedValue instanceof BSONDocument && self::isOperator($expectedValue)) {
+                $operatorName = self::getOperatorName($expectedValue);
+
+                if ($operatorName === '$$exists') {
+                    Assert::assertIsBool($expectedValue['$$exists'], '$$exists requires bool');
+
+                    if ($expectedValue['$$exists'] && ! $actualKeyExists) {
+                        self::failAt(sprintf('$actual does not have expected key "%s"', $key), $keyPath);
+                    }
+
+                    if (! $expectedValue['$$exists'] && $actualKeyExists) {
+                        self::failAt(sprintf('$actual has unexpected key "%s"', $key), $keyPath);
+                    }
+
+                    continue;
+                }
+
+                if ($operatorName === '$$unsetOrMatches') {
+                    if (! $actualKeyExists) {
+                        continue;
+                    }
+
+                    $expectedValue = $expectedValue['$$unsetOrMatches'];
+                }
+            }
+
+            if (! $actualKeyExists) {
+                self::failAt(sprintf('$actual does not have expected key "%s"', $key), $keyPath);
+            }
+
+            $this->assertMatches(
+                $expectedValue,
+                $actual[$key],
+                (empty($keyPath) ? $key : $keyPath . '.' . $key)
+            );
+        }
+
+        // Ignore extra keys in root documents
+        if ($this->allowExtraKeys || ($this->allowExtraRootKeys && empty($keyPath))) {
+            return;
+        }
+
+        foreach ($actual as $key => $_) {
+            if (! $expected->offsetExists($key)) {
+                self::failAt(sprintf('$actual has unexpected key "%s"', $key), $keyPath);
+            }
+        }
+    }
+
+    private function assertMatchesOperator(BSONDocument $operator, $actual, $keyPath)
+    {
+        $name = self::getOperatorName($operator);
+
+        if ($name === '$$unsetOrMatches') {
+            /* If the operator is used at the top level, consider null values
+             * for $actual to be unset. If the operator is nested, this check is
+             * done later during document iteration. */
+            if ($keyPath === '' && $actual === null) {
+                return;
+            }
+
+            $this->assertMatches(
+                self::prepare($operator['$$unsetOrMatches']),
+                $actual,
+                $keyPath
+            );
+
+            return;
+        }
+
+        throw new LogicException('unsupported operator: ' . $name);
+    }
+
+    /** @see ConstraintTrait */
+    private function doAdditionalFailureDescription($other)
+    {
+        if ($this->lastFailure === null) {
+            return '';
+        }
+
+        return $this->lastFailure->getMessage();
+    }
+
+    /** @see ConstraintTrait */
+    private function doFailureDescription($other)
+    {
+        return 'expected value matches actual value';
+    }
+
+    /** @see ConstraintTrait */
+    private function doMatches($other)
+    {
+        $other = self::prepare($other);
+
+        try {
+            $this->assertMatches($this->value, $other);
+        } catch (RuntimeException $e) {
+            return false;
+        }
+
+        return true;
+    }
+
+    /** @see ConstraintTrait */
+    private function doToString()
+    {
+        return 'matches ' . $this->exporter()->export($this->value);
+    }
+
+    private static function failAt(string $message, string $keyPath)
+    {
+        $prefix = empty($keyPath) ? '' : sprintf('Field path "%s": ', $keyPath);
+
+        throw new RuntimeException($prefix . $message);
+    }
+
+    private static function getOperatorName(BSONDocument $document)
+    {
+        foreach ($document as $key => $_) {
+            if (strpos((string) $key, '$$') === 0) {
+                return $key;
+            }
+        }
+
+        throw new LogicException('should not reach this point');
+    }
+
+    private static function isNumeric($value)
+    {
+        return is_int($value) || is_float($value) || $value instanceof Int64;
+    }
+
+    private static function isOperator(BSONDocument $document)
+    {
+        if (count($document) !== 1) {
+            return false;
+        }
+
+        foreach ($document as $key => $_) {
+            return strpos((string) $key, '$$') === 0;
+        }
+
+        throw new LogicException('should not reach this point');
+    }
+
+    /**
+     * Prepare a value for comparison.
+     *
+     * If the value is an array or object, it will be converted to a BSONArray
+     * or BSONDocument. If $value is an array and $isRoot is true, it will be
+     * converted to a BSONDocument; otherwise, it will be converted to a
+     * BSONArray or BSONDocument based on its keys. Each value within an array
+     * or document will then be prepared recursively.
+     *
+     * @param mixed $bson
+     * @return mixed
+     */
+    private static function prepare($bson)
+    {
+        if (! is_array($bson) && ! is_object($bson)) {
+            return $bson;
+        }
+
+        /* Convert Int64 objects to integers on 64-bit platforms for
+         * compatibility reasons. */
+        if ($bson instanceof Int64 && PHP_INT_SIZE != 4) {
+            return (int) ((string) $bson);
+        }
+
+        /* TODO: Convert Int64 objects to integers on 32-bit platforms if they
+         * can be expressed as such. This is necessary to handle flexible
+         * numeric comparisons if the server returns 32-bit value as a 64-bit
+         * integer (e.g. cursor ID). */
+
+        // Serializable can produce an array or object, so recurse on its output
+        if ($bson instanceof Serializable) {
+            return self::prepare($bson->bsonSerialize());
+        }
+
+        /* Serializable has already been handled, so any remaining instances of
+         * Type will not serialize as BSON arrays or objects */
+        if ($bson instanceof Type) {
+            return $bson;
+        }
+
+        if (is_array($bson) && self::isArrayEmptyOrIndexed($bson)) {
+            $bson = new BSONArray($bson);
+        }
+
+        if (! $bson instanceof BSONArray && ! $bson instanceof BSONDocument) {
+            /* If $bson is an object, any numeric keys may become inaccessible.
+             * We can work around this by casting back to an array. */
+            $bson = new BSONDocument((array) $bson);
+        }
+
+        foreach ($bson as $key => $value) {
+            if (is_array($value) || is_object($value)) {
+                $bson[$key] = self::prepare($value);
+            }
+        }
+
+        return $bson;
+    }
+
+    private static function isArrayEmptyOrIndexed(array $a)
+    {
+        if (empty($a)) {
+            return true;
+        }
+
+        return array_keys($a) === range(0, count($a) - 1);
+    }
+}
diff --git a/tests/Alcaeus/MongoDbAdapter/Constraint/README.md b/tests/Alcaeus/MongoDbAdapter/Constraint/README.md
new file mode 100644
index 00000000..36745fe8
--- /dev/null
+++ b/tests/Alcaeus/MongoDbAdapter/Constraint/README.md
@@ -0,0 +1,6 @@
+Document Constraints for PHPUnit
+================================
+
+The constraints in this directory have been copied from the MongoDB Library at
+https://github.com/mongodb/mongo-php-library. This code is licensed under the
+Apache License Version 2.0.
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoBinDataTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoBinDataTest.php
index c6fbac9e..5b2abb1b 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoBinDataTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoBinDataTest.php
@@ -15,10 +15,10 @@ class MongoBinDataTest extends TestCase
     public function testCreate()
     {
         $bin = new \MongoBinData(self::GUID, \MongoBinData::FUNC);
-        $this->assertAttributeSame(self::GUID, 'bin', $bin);
-        $this->assertAttributeSame(\MongoBinData::FUNC, 'type', $bin);
+        $this->assertSame(self::GUID, $bin->bin);
+        $this->assertSame(\MongoBinData::FUNC, $bin->type);
 
-        $this->assertSame('<Mongo Binary Data>', (string)$bin);
+        $this->assertSame('<Mongo Binary Data>', (string) $bin);
 
         return $bin;
     }
@@ -44,7 +44,7 @@ public function testCreateWithBsonBinary()
         $bsonBinary = new \MongoDB\BSON\Binary(self::GUID, \MongoDB\BSON\Binary::TYPE_UUID);
         $bin = new \MongoBinData($bsonBinary);
 
-        $this->assertAttributeSame(self::GUID, 'bin', $bin);
-        $this->assertAttributeSame(\MongoBinData::UUID_RFC4122, 'type', $bin);
+        $this->assertSame(self::GUID, $bin->bin);
+        $this->assertSame(\MongoBinData::UUID_RFC4122, $bin->type);
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoClientTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoClientTest.php
index d0edc4dd..de13f786 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoClientTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoClientTest.php
@@ -9,9 +9,25 @@
  */
 class MongoClientTest extends TestCase
 {
+    /**
+     * @dataProvider provideConnectionUri
+     */
+    public function testConnectionUri($uri, $expected)
+    {
+        $this->skipTestIf(extension_loaded('mongo'));
+        $this->assertSame($expected, (string) (new \MongoClient($uri, ['connect' => false])));
+    }
+
+    public function provideConnectionUri()
+    {
+        yield ['default', sprintf('mongodb://%s:%d', \MongoClient::DEFAULT_HOST, \MongoClient::DEFAULT_PORT)];
+        yield ['localhost', 'mongodb://localhost'];
+        yield ['mongodb://localhost', 'mongodb://localhost'];
+    }
+
     public function testSerialize()
     {
-        $this->assertInternalType('string', serialize($this->getClient()));
+        $this->assertIsString(serialize($this->getClient()));
     }
 
     public function testGetDb()
@@ -58,7 +74,7 @@ public function testGetHosts()
     {
         $client = $this->getClient();
         $hosts = $client->getHosts();
-        $this->assertArraySubset(
+        $this->assertMatches(
             [
                 'localhost:27017;-;.;' . getmypid() => [
                     'host' => 'localhost',
@@ -74,7 +90,7 @@ public function testGetHosts()
     public function testGetHostsExceptionHandling()
     {
         $this->expectException(\MongoConnectionException::class);
-        $this->expectExceptionMessageRegExp('/fake_host/');
+        $this->expectErrorMessageMatches('/fake_host/');
 
         $client = $this->getClient(null, 'mongodb://fake_host');
         $client->getHosts();
@@ -246,7 +262,7 @@ public function testConnectWithUsernameAndPassword()
 
         $collection->insert($document);
     }
-    
+
     public function testConnectWithUsernameAndPasswordInConnectionUrl()
     {
         $this->expectException(\MongoConnectionException::class);
@@ -260,6 +276,13 @@ public function testConnectWithUsernameAndPasswordInConnectionUrl()
         $collection->insert($document);
     }
 
+    public function testConnectionUriOptionIntegerTypeCasting()
+    {
+        $client = new \MongoClient('mongodb://localhost/db?w=0&wtimeout=0', ['connect' => false]);
+
+        $this->assertSame(['w' => 0, 'wtimeout' => 0], $client->getWriteConcern());
+    }
+
     /**
      * @param array $options
      * @return string
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCodeTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCodeTest.php
index b55568f9..11a593f6 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCodeTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCodeTest.php
@@ -4,6 +4,7 @@
 
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
 use Alcaeus\MongoDbAdapter\TypeInterface;
+use ReflectionProperty;
 
 /**
  * @author alcaeus <alcaeus@alcaeus.org>
@@ -13,23 +14,49 @@ class MongoCodeTest extends TestCase
     public function testCreate()
     {
         $code = new \MongoCode('code', ['scope' => 'bleh']);
-        $this->assertAttributeSame('code', 'code', $code);
-        $this->assertAttributeSame(['scope' => 'bleh'], 'scope', $code);
 
-        $this->assertSame('code', (string)$code);
+        $this->assertSame('code', $this->getAttributeValue($code, 'code'));
+        $this->assertSame(['scope' => 'bleh'], $this->getAttributeValue($code, 'scope'));
+
+        $this->assertSame('code', (string) $code);
 
         return $code;
     }
 
-    /**
-     * @depends testCreate
-     */
-    public function testConvertToBson(\MongoCode $code)
+    public function testCreateWithoutScope()
+    {
+        $code = new \MongoCode('code');
+
+        $this->assertSame('code', $this->getAttributeValue($code, 'code'));
+        $this->assertSame([], $this->getAttributeValue($code, 'scope'));
+
+        $this->assertSame('code', (string) $code);
+
+        return $code;
+    }
+
+    public function testConvertToBson()
+    {
+        $code = new \MongoCode('code', ['scope' => 'bleh']);
+
+        $this->skipTestUnless($code instanceof TypeInterface);
+
+        $bsonCode = $code->toBSONType();
+        $this->assertInstanceOf('MongoDB\BSON\Javascript', $bsonCode);
+        $this->assertSame('code', $bsonCode->getCode());
+        $this->assertEquals((object) ['scope' => 'bleh'], $bsonCode->getScope());
+    }
+
+    public function testConvertToBsonWithoutScope()
     {
+        $code = new \MongoCode('code');
+
         $this->skipTestUnless($code instanceof TypeInterface);
 
         $bsonCode = $code->toBSONType();
         $this->assertInstanceOf('MongoDB\BSON\Javascript', $bsonCode);
+        $this->assertSame('code', $bsonCode->getCode());
+        $this->assertNull($bsonCode->getScope());
     }
 
     public function testCreateWithBsonObject()
@@ -39,7 +66,15 @@ public function testCreateWithBsonObject()
         $bsonCode = new \MongoDB\BSON\Javascript('code', ['scope' => 'bleh']);
         $code = new \MongoCode($bsonCode);
 
-        $this->assertAttributeSame('code', 'code', $code);
-        $this->assertAttributeSame(['scope' => 'bleh'], 'scope', $code);
+        $this->assertSame('code', $this->getAttributeValue($code, 'code'));
+        $this->assertSame(['scope' => 'bleh'], $this->getAttributeValue($code, 'scope'));
+    }
+
+    private function getAttributeValue(\MongoCode $code, $attribute)
+    {
+        $property = new ReflectionProperty($code, $attribute);
+        $property->setAccessible(true);
+
+        return $property->getValue($code);
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCollectionTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCollectionTest.php
index 5f533d23..501cbdf0 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCollectionTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCollectionTest.php
@@ -2,10 +2,14 @@
 
 namespace Alcaeus\MongoDbAdapter\Tests\Mongo;
 
+use ArrayObject;
 use MongoDB\BSON\Regex;
 use MongoDB\Driver\ReadPreference;
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
+use MongoId;
 use PHPUnit\Framework\Error\Warning;
+use function extension_loaded;
+use function strcasecmp;
 
 /**
  * @author alcaeus <alcaeus@alcaeus.org>
@@ -14,7 +18,7 @@ class MongoCollectionTest extends TestCase
 {
     public function testSerialize()
     {
-        $this->assertInternalType('string', serialize($this->getCollection()));
+        $this->assertIsString(serialize($this->getCollection()));
     }
 
     public function testGetNestedCollections()
@@ -44,19 +48,17 @@ public function testCreateRecord()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $object);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $object->_id);
         $this->assertSame($id, (string) $object->_id);
-        $this->assertObjectHasAttribute('foo', $object);
-        $this->assertAttributeSame('bar', 'foo', $object);
+        $this->assertNotNull($object->foo);
+        $this->assertSame('bar', $object->foo);
     }
 
     public function testInsertInvalidData()
     {
         // Dirty hack to support both PHPUnit 5.x and 6.x
-        $className = class_exists(Warning::class) ? Warning::class : \PHPUnit_Framework_Error_Warning::class;
-        $this->expectException($className);
-
-        $this->expectExceptionMessage('MongoCollection::insert(): expects parameter 1 to be an array or object, integer given');
+        $this->expectWarning();
+        $this->expectWarningMessage('MongoCollection::insert(): expects parameter 1 to be an array or object, integer given');
 
         $document = 8;
         $this->getCollection()->insert($document);
@@ -78,6 +80,34 @@ public function testInsertArrayWithNumericKeys()
         $this->assertSame(1, $this->getCollection()->count(['_id' => $document['_id']]));
     }
 
+    /**
+     * @dataProvider emptyIdProvider
+     */
+    public function testInsertArrayWithEmptyIds($id)
+    {
+        $document = ['_id' => $id];
+        $this->getCollection()->insert($document);
+
+        $this->assertSame(1, $this->getCollection()->count(['_id' => $id]));
+    }
+
+    public function emptyIdProvider()
+    {
+        return [
+            'Zero as string' => ['0'],
+            'Zero as int' => [0],
+            'Empty string' => [''],
+        ];
+    }
+
+    public function testInsertArrayWithEmptyId()
+    {
+        $document = ['_id' => ''];
+        $this->getCollection()->insert($document);
+
+        $this->assertSame(1, $this->getCollection()->count(['_id' => $document['_id']]));
+    }
+
     public function testInsertEmptyObject()
     {
         $document = (object) [];
@@ -95,6 +125,15 @@ public function testInsertObjectWithPrivateProperties()
         $this->getCollection()->insert($document);
     }
 
+    public function testInsertArrayObjectWithProtectedProperties()
+    {
+        $document = new ArrayObjectWithProtectedProperties(['foo' => 'bar']);
+        $this->getCollection()->insert($document);
+
+        $this->assertInstanceOf('MongoId', $document['_id']);
+        $this->assertEquals(['_id' => $document['_id'], 'foo' => 'bar'], $this->getCollection()->findOne(['_id' => $document['_id']]));
+    }
+
     public function testInsertWithInvalidKey()
     {
         $document = ['*' => 'foo'];
@@ -130,6 +169,20 @@ public function testInsertWithNumericKey()
         $this->assertSame(1, $this->getCollection()->count(['foo']));
     }
 
+    public function testInsertWithAlphaNumericKey()
+    {
+        /**
+         * Force the array to store the key as a string "0".
+         * Initialising like ['0' => 'foo'] casts the string to an int.
+         */
+        $document = new \stdClass();
+        $document->{'0'} = 'foo';
+        $document = (array) $document;
+
+        $this->getCollection()->insert($document);
+        $this->assertSame(1, $this->getCollection()->count(['0' => 'foo']));
+    }
+
     public function testInsertDuplicate()
     {
         $collection = $this->getCollection();
@@ -142,7 +195,7 @@ public function testInsertDuplicate()
         unset($document['_id']);
 
         $this->expectException(\MongoDuplicateKeyException::class);
-        $this->expectExceptionMessageRegExp('/E11000 duplicate key error .* mongo-php-adapter\.test/');
+        $this->expectErrorMessageMatches('/E11000 duplicate key error .* mongo-php-adapter\.test/');
         $this->expectExceptionCode(11000);
         $collection->insert($document);
     }
@@ -196,7 +249,7 @@ public function testInsertMany()
             ['foo' => 'bar'],
             ['bar' => 'foo']
         ];
-        $this->assertArraySubset($expected, $this->getCollection()->batchInsert($documents));
+        $this->assertMatches($expected, $this->getCollection()->batchInsert($documents));
 
         foreach ($documents as $document) {
             $this->assertInstanceOf('MongoId', $document['_id']);
@@ -218,7 +271,7 @@ public function testInsertManyWithNonNumericKeys()
             'a' => ['foo' => 'bar'],
             'b' => ['bar' => 'foo']
         ];
-        $this->assertArraySubset($expected, $this->getCollection()->batchInsert($documents));
+        $this->assertMatches($expected, $this->getCollection()->batchInsert($documents));
 
         $newCollection = $this->getCheckDatabase()->selectCollection('test');
         $this->assertSame(2, $newCollection->count());
@@ -238,7 +291,7 @@ public function testBatchInsertContinuesOnError()
             8,
             'b' => ['bar' => 'foo']
         ];
-        $this->assertArraySubset($expected, $this->getCollection()->batchInsert($documents, ['continueOnError' => true]));
+        $this->assertMatches($expected, $this->getCollection()->batchInsert($documents, ['continueOnError' => true]));
 
         $newCollection = $this->getCheckDatabase()->selectCollection('test');
         $this->assertSame(1, $newCollection->count());
@@ -250,7 +303,7 @@ public function testBatchInsertException()
         $documents = [['_id' => $id, 'foo' => 'bar'], ['_id' => $id, 'foo' => 'bleh']];
 
         $this->expectException(\MongoDuplicateKeyException::class);
-        $this->expectExceptionMessageRegExp('/E11000 duplicate key error .* mongo-php-adapter.test.*_id_/');
+        $this->expectErrorMessageMatches('/E11000 duplicate key error .* mongo-php-adapter.test.*_id_/');
         $this->expectExceptionCode(11000);
 
         $this->getCollection()->batchInsert($documents);
@@ -362,7 +415,7 @@ public function testUpdateReplaceOne()
     public function testUpdateReplaceMultiple()
     {
         $this->expectException(\MongoWriteConcernException::class);
-        $this->expectExceptionMessageRegExp('/multi update only works with \$ operators/', 9);
+        $this->expectErrorMessageMatches('/multi update only works with \$ operators/', 9);
         $this->getCollection()->update(['foo' => 'bar'], ['foo' => 'foo'], ['multiple' => true]);
     }
 
@@ -552,7 +605,7 @@ public function testFindWithProjection($projection)
         foreach ($cursor as $document) {
             $this->assertCount(2, $document);
             $this->assertArrayHasKey('_id', $document);
-            $this->assertArraySubset(['bar' => 'bar'], $document);
+            $this->assertMatches(['bar' => 'bar'], $document);
         }
     }
 
@@ -614,7 +667,7 @@ public function testFindWithProjectionExcludeId($projection)
         foreach ($cursor as $document) {
             $this->assertCount(1, $document);
             $this->assertArrayNotHasKey('_id', $document);
-            $this->assertArraySubset(['bar' => 'bar'], $document);
+            $this->assertMatches(['bar' => 'bar'], $document);
         }
     }
 
@@ -714,7 +767,7 @@ public function testFindOneWithProjection()
 
         $document = $this->getCollection()->findOne(['foo' => 'foo'], ['bar' => true]);
         $this->assertCount(2, $document);
-        $this->assertArraySubset(['bar' => 'bar'], $document);
+        $this->assertMatches(['bar' => 'bar'], $document);
     }
 
     public function testFindOneWithLegacyProjection()
@@ -724,7 +777,7 @@ public function testFindOneWithLegacyProjection()
 
         $document = $this->getCollection()->findOne(['foo' => 'foo'], ['bar']);
         $this->assertCount(2, $document);
-        $this->assertArraySubset(['bar' => 'bar'], $document);
+        $this->assertMatches(['bar' => 'bar'], $document);
     }
 
     public function testFindOneNotFound()
@@ -748,7 +801,7 @@ public function testDistinct()
         $this->prepareData();
 
         $values = $this->getCollection()->distinct('foo');
-        $this->assertInternalType('array', $values);
+        $this->assertIsArray($values);
 
         sort($values);
         $this->assertEquals(['bar', 'foo'], $values);
@@ -759,7 +812,7 @@ public function testDistinctWithQuery()
         $this->prepareData();
 
         $values = $this->getCollection()->distinct('foo', ['foo' => 'bar']);
-        $this->assertInternalType('array', $values);
+        $this->assertIsArray($values);
         $this->assertEquals(['bar'], $values);
     }
 
@@ -791,6 +844,8 @@ public function testDistinctWithIdQuery()
 
     public function testAggregate()
     {
+        $this->skipTestIf(extension_loaded('mongo'));
+
         $collection = $this->getCollection();
 
         $this->prepareData();
@@ -807,8 +862,8 @@ public function testAggregate()
             ]
         ];
 
-        $result = $collection->aggregate($pipeline);
-        $this->assertInternalType('array', $result);
+        $result = $collection->aggregate($pipeline, ['cursor' => true]);
+        $this->assertIsArray($result);
         $this->assertArrayHasKey('result', $result);
 
         $this->assertEquals([
@@ -819,6 +874,8 @@ public function testAggregate()
 
     public function testAggregateWithMultiplePilelineOperatorsAsArguments()
     {
+        $this->skipTestIf(version_compare($this->getServerVersion(), '3.6.0', '>='), 'Test does not apply to MongoDB >= 3.6.');
+
         $collection = $this->getCollection();
 
         $this->prepareData();
@@ -842,7 +899,7 @@ public function testAggregateWithMultiplePilelineOperatorsAsArguments()
             $this->fail($msg);
         }
 
-        $this->assertInternalType('array', $result);
+        $this->assertIsArray($result);
         $this->assertArrayHasKey('result', $result);
 
         $this->assertEquals([
@@ -853,6 +910,8 @@ public function testAggregateWithMultiplePilelineOperatorsAsArguments()
 
     public function testAggregateInvalidPipeline()
     {
+        $this->skipTestIf(extension_loaded('mongo'));
+
         $collection = $this->getCollection();
 
         $pipeline = [
@@ -863,7 +922,7 @@ public function testAggregateInvalidPipeline()
 
         $this->expectException(\MongoResultException::class);
         $this->expectExceptionMessage('Unrecognized pipeline stage name');
-        $collection->aggregate($pipeline);
+        $collection->aggregate($pipeline, ['cursor' => true]);
     }
 
     public function testAggregateTimeoutException()
@@ -886,7 +945,7 @@ public function testAggregateTimeoutException()
             ]
         ];
 
-        $collection->aggregate($pipeline, ['maxTimeMS' => 1]);
+        $collection->aggregate($pipeline, ['maxTimeMS' => 1, 'cursor' => true]);
     }
 
     public function testAggregateCursor()
@@ -930,7 +989,7 @@ public function testReadPreference()
         $this->assertSame(['type' => \MongoClient::RP_SECONDARY_PREFERRED, 'tagsets' => [['a' => 'b']]], $collection->getReadPreference());
 
         $this->assertTrue($collection->setSlaveOkay(false));
-        $this->assertArraySubset(['type' => \MongoClient::RP_PRIMARY], $collection->getReadPreference());
+        $this->assertMatches(['type' => \MongoClient::RP_PRIMARY], $collection->getReadPreference());
     }
 
     public function testReadPreferenceIsSetInDriver()
@@ -1012,10 +1071,9 @@ public function testSaveInsert()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $object);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $object->_id);
         $this->assertSame($id, (string) $object->_id);
-        $this->assertObjectHasAttribute('foo', $object);
-        $this->assertAttributeSame('bar', 'foo', $object);
+        $this->assertSame('bar', $object->foo);
     }
 
     public function testRemoveOne()
@@ -1055,13 +1113,13 @@ public function testSaveUpdate()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $object);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $object->_id);
         $this->assertSame($id, (string) $object->_id);
-        $this->assertObjectHasAttribute('foo', $object);
-        $this->assertAttributeSame('foo', 'foo', $object);
+        $this->assertSame('foo', $object->foo);
     }
 
-    public function testSavingShouldReplaceTheWholeDocument() {
+    public function testSavingShouldReplaceTheWholeDocument()
+    {
         $id = '54203e08d51d4a1f868b456e';
         $collection = $this->getCollection();
 
@@ -1076,7 +1134,7 @@ public function testSavingShouldReplaceTheWholeDocument() {
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertObjectNotHasAttribute('foo', $object);
+        $this->assertArrayNotHasKey('bar', $object);
     }
 
     public function testSaveDuplicate()
@@ -1339,8 +1397,8 @@ public function testDeleteIndexUsingIndexName()
             $expected['code'] = 27;
         }
 
-        // Using assertArraySubset because newer versions (3.4.7?) also return `codeName`
-        $this->assertArraySubset($expected, $this->getCollection()->deleteIndex('bar'));
+        // Using assertMatches because newer versions (3.4.7?) also return `codeName`
+        $this->assertMatches($expected, $this->getCollection()->deleteIndex('bar'));
 
         $this->assertCount(2, iterator_to_array($newCollection->listIndexes()));
     }
@@ -1390,17 +1448,14 @@ public function testDeleteIndexes()
 
     public function testDeleteIndexesForNonExistingCollection()
     {
-        $expected = [
-            'ok' => 0.0,
-            'errmsg' => 'ns not found',
-        ];
+        $result = $this->getCollection('nonExisting')->deleteIndexes();
 
+        $this->assertSame(0.0, $result['ok']);
+        $this->assertMatchesRegularExpression('#ns not found#', $result['errmsg']);
         if (version_compare($this->getServerVersion(), '3.4.0', '>=')) {
+            $this->assertSame(26, $result['code']);
             $expected['code'] = 26;
         }
-
-        // Using assertArraySubset because newer versions (3.4.7?) also return `codeName`
-        $this->assertArraySubset($expected, $this->getCollection('nonExisting')->deleteIndexes());
     }
 
     public function dataGetIndexInfo()
@@ -1551,7 +1606,7 @@ public function testFindAndModifyUpdate()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeSame('foo', 'foo', $object);
+        $this->assertSame('foo', $object->foo);
     }
 
     public function testFindAndModifyUpdateWithUpdateOptions()
@@ -1576,8 +1631,8 @@ public function testFindAndModifyUpdateWithUpdateOptions()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeSame('foo', 'bar', $object);
-        $this->assertObjectNotHasAttribute('foo', $object);
+        $this->assertSame('foo', $object->bar);
+        $this->assertArrayNotHasKey('foo', $object);
     }
 
     public function testFindAndModifyWithUpdateParamAndOption()
@@ -1605,8 +1660,8 @@ public function testFindAndModifyWithUpdateParamAndOption()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeSame('foobar', 'foo', $object);
-        $this->assertObjectNotHasAttribute('bar', $object);
+        $this->assertSame('foobar', $object->foo);
+        $this->assertArrayNotHasKey('bar', $object);
     }
 
     public function testFindAndModifyUpdateReplace()
@@ -1627,8 +1682,8 @@ public function testFindAndModifyUpdateReplace()
         $object = $newCollection->findOne();
 
         $this->assertNotNull($object);
-        $this->assertAttributeSame('boo', 'foo', $object);
-        $this->assertObjectNotHasAttribute('bar', $object);
+        $this->assertSame('boo', $object->foo);
+        $this->assertArrayNotHasKey('bar', $object);
     }
 
     public function testFindAndModifyUpdateReturnNew()
@@ -1669,6 +1724,8 @@ public function testFindAndModifyWithFields()
 
     public function testGroup()
     {
+        $this->skipTestIf(version_compare($this->getServerVersion(), '4.2.0', '>='), 'Test does not apply to MongoDB >= 4.2.');
+
         $collection = $this->getCollection();
 
         $document1 = ['a' => 2];
@@ -1684,7 +1741,7 @@ public function testGroup()
 
         $result = $collection->group($keys, $initial, $reduce, $condition);
 
-        $this->assertArraySubset(
+        $this->assertMatches(
             [
                 'retval' => [['count' => 1.0]],
                 'count' => 1.0,
@@ -1740,7 +1797,7 @@ public function testMapReduce()
             'map' => new \MongoCode($map),
             'reduce' => new \MongoCode($reduce),
             'query' => (object) [],
-            'out' => ['inline' => true],
+            'out' => ['inline' => 1],
             'finalize' => new \MongoCode($finalize),
         ];
 
@@ -1765,8 +1822,12 @@ public function testMapReduce()
             ],
         ];
 
+        usort($result['results'], function ($a, $b) {
+            return strcasecmp($a['_id'], $b['_id']);
+        });
+
         $this->assertSame(1.0, $result['ok']);
-        $this->assertSame($expected, $result['results']);
+        $this->assertEquals($expected, $result['results']);
     }
 
     public function testFindAndModifyResultException()
@@ -1828,12 +1889,11 @@ public function testValidate()
         $collection->insert($document);
         $result = $collection->validate();
 
-        $this->assertArraySubset(
+        $this->assertMatches(
             [
                 'ns' => 'mongo-php-adapter.test',
                 'nrecords' => 1,
                 'nIndexes' => 1,
-                'keysPerIndex' => ['mongo-php-adapter.test.$_id_' => 1],
                 'valid' => true,
                 'errors' => [],
             ],
@@ -1850,7 +1910,7 @@ public function testDrop()
             'nIndexesWas' => 1,
             'ok' => 1.0
         ];
-        $this->assertSame($expected, $this->getCollection()->drop());
+        $this->assertEquals($expected, $this->getCollection()->drop());
     }
 
     public function testEmptyCollectionName()
@@ -1976,3 +2036,8 @@ class PrivatePropertiesStub
 {
     private $foo = 'bar';
 }
+
+class ArrayObjectWithProtectedProperties extends ArrayObject
+{
+    protected $something = 'baz';
+}
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCommandCursorTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCommandCursorTest.php
index e5a8d5c3..3d557608 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCommandCursorTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCommandCursorTest.php
@@ -2,6 +2,7 @@
 
 namespace Alcaeus\MongoDbAdapter\Tests\Mongo;
 
+use MongoCursorInterface;
 use MongoDB\Database;
 use MongoDB\Driver\ReadPreference;
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
@@ -15,7 +16,7 @@ public function testSerialize()
     {
         $this->prepareData();
         $cursor = $this->getCollection()->aggregateCursor([['$match' => ['foo' => 'bar']]]);
-        $this->assertInternalType('string', serialize($cursor));
+        $this->assertIsString(serialize($cursor));
     }
 
     public function testInfo()
@@ -58,7 +59,7 @@ public function testInfo()
             'connection_type_desc' => 'STANDALONE',
         ];
 
-        $this->assertArraySubset($expected, $cursor->info());
+        $this->assertMatches($expected, $cursor->info());
 
         $i = 0;
         foreach ($array as $key => $value) {
@@ -136,7 +137,7 @@ public function dataCommandAppliesCorrectReadPreference()
             'mapReduceWithOutInline' => [
                 [
                     'mapReduce' => (string) $this->getCollection(),
-                    'out' => ['inline' => true],
+                    'out' => ['inline' => 1],
                 ],
                 ReadPreference::RP_SECONDARY,
             ],
@@ -202,4 +203,12 @@ public function dataCommandAppliesCorrectReadPreference()
             ],
         ];
     }
+
+    public function testInterfaces()
+    {
+        $this->prepareData();
+        $cursor = $this->getCollection()->aggregateCursor([['$match' => ['foo' => 'bar']]]);
+
+        $this->assertInstanceOf(MongoCursorInterface::class, $cursor);
+    }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCursorTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCursorTest.php
index abc1bdde..d2af27fb 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCursorTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoCursorTest.php
@@ -4,6 +4,8 @@
 
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
 use Alcaeus\MongoDbAdapter\TypeConverter;
+use Countable;
+use MongoCursorInterface;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Model\BSONDocument;
 use MongoDB\Operation\Find;
@@ -17,7 +19,7 @@ public function testSerialize()
     {
         $this->prepareData();
         $cursor = $this->getCollection()->find(['foo' => 'bar']);
-        $this->assertInternalType('string', serialize($cursor));
+        $this->assertIsString(serialize($cursor));
     }
 
     public function testCursorConvertsTypes()
@@ -200,7 +202,8 @@ public function testCursorAppliesOptions($checkOptionCallback, \Closure $applyOp
 
     public static function getCursorOptions()
     {
-        function getMissingOptionCallback($optionName) {
+        function getMissingOptionCallback($optionName)
+        {
             return function ($value) use ($optionName) {
                 return
                     is_array($value) &&
@@ -208,7 +211,8 @@ function getMissingOptionCallback($optionName) {
             };
         }
 
-        function getBasicCheckCallback($expected, $optionName) {
+        function getBasicCheckCallback($expected, $optionName)
+        {
             return function ($value) use ($expected, $optionName) {
                 return
                     is_array($value) &&
@@ -217,7 +221,8 @@ function getBasicCheckCallback($expected, $optionName) {
             };
         }
 
-        function getModifierCheckCallback($expected, $modifierName) {
+        function getModifierCheckCallback($expected, $modifierName)
+        {
             return function ($value) use ($expected, $modifierName) {
                 return
                     is_array($value) &&
@@ -429,23 +434,23 @@ public function testExplain()
                 'parsedQuery' => [
                     'foo' => ['$eq' => 'bar']
                 ],
-                'winningPlan' => [],
-                'rejectedPlans' => [],
+                'winningPlan' => ['$$exists' => true],
+                'rejectedPlans' => ['$$exists' => true],
             ],
             'executionStats' => [
                 'executionSuccess' => true,
                 'nReturned' => 1,
                 'totalKeysExamined' => 0,
                 'totalDocsExamined' => 3,
-                'executionStages' => [],
-                'allPlansExecution' => [],
+                'executionStages' => ['$$exists' => true],
+                'allPlansExecution' => ['$$exists' => true],
             ],
             'serverInfo' => [
                 'port' => 27017,
             ],
         ];
 
-        $this->assertArraySubset($expected, $cursor->explain());
+        $this->assertMatches($expected, $cursor->explain());
     }
 
     public function testExplainWithEmptyProjection()
@@ -463,23 +468,23 @@ public function testExplainWithEmptyProjection()
                 'parsedQuery' => [
                     'foo' => ['$eq' => 'bar']
                 ],
-                'winningPlan' => [],
-                'rejectedPlans' => [],
+                'winningPlan' => ['$$exists' => true],
+                'rejectedPlans' => ['$$exists' => true],
             ],
             'executionStats' => [
                 'executionSuccess' => true,
                 'nReturned' => 2,
                 'totalKeysExamined' => 0,
                 'totalDocsExamined' => 3,
-                'executionStages' => [],
-                'allPlansExecution' => [],
+                'executionStages' => ['$$exists' => true],
+                'allPlansExecution' => ['$$exists' => true],
             ],
             'serverInfo' => [
                 'port' => 27017,
             ],
         ];
 
-        $this->assertArraySubset($expected, $cursor->explain());
+        $this->assertMatches($expected, $cursor->explain());
     }
 
     public function testExplainConvertsQuery()
@@ -494,23 +499,36 @@ public function testExplainConvertsQuery()
                 'plannerVersion' => 1,
                 'namespace' => 'mongo-php-adapter.test',
                 'indexFilterSet' => false,
-                'winningPlan' => [],
-                'rejectedPlans' => [],
+                'winningPlan' => ['$$exists' => true],
+                'rejectedPlans' => ['$$exists' => true],
             ],
             'executionStats' => [
                 'executionSuccess' => true,
                 'nReturned' => 2,
                 'totalKeysExamined' => 0,
                 'totalDocsExamined' => 3,
-                'executionStages' => [],
-                'allPlansExecution' => [],
+                'executionStages' => ['$$exists' => true],
+                'allPlansExecution' => ['$$exists' => true],
             ],
             'serverInfo' => [
                 'port' => 27017,
             ],
         ];
 
-        $this->assertArraySubset($expected, $cursor->explain());
+        $this->assertMatches($expected, $cursor->explain());
+    }
+
+    public function testInterfaces()
+    {
+        $collection = $this->getCollection();
+        $cursor = $collection->find();
+
+        $this->assertInstanceOf(MongoCursorInterface::class, $cursor);
+
+        // The countable interface is necessary for compatibility with PHP 7.3+, but not implemented by MongoCursor
+        if (! extension_loaded('mongo')) {
+            $this->assertInstanceOf(Countable::class, $cursor);
+        }
     }
 
 
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBRefTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBRefTest.php
index ba39c8ca..fb5000b8 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBRefTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBRefTest.php
@@ -85,7 +85,7 @@ public function testGet()
         $db->selectCollection('test')->insert($document);
 
         $fetchedRef = \MongoDBRef::get($db, ['$ref' => 'test', '$id' => $id]);
-        $this->assertInternalType('array', $fetchedRef);
+        $this->assertIsArray($fetchedRef);
         $this->assertEquals($document, $fetchedRef);
     }
 
@@ -99,7 +99,7 @@ public function testGetThroughMongoDB()
         $db->selectCollection('test')->insert($document);
 
         $fetchedRef = $db->getDBRef(['$ref' => 'test', '$id' => $id]);
-        $this->assertInternalType('array', $fetchedRef);
+        $this->assertIsArray($fetchedRef);
         $this->assertEquals($document, $fetchedRef);
     }
 
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBTest.php
index 1636341e..9b7d18db 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDBTest.php
@@ -12,7 +12,7 @@ class MongoDBTest extends TestCase
 {
     public function testSerialize()
     {
-        $this->assertInternalType('string', serialize($this->getDatabase()));
+        $this->assertIsString(serialize($this->getDatabase()));
     }
 
     public function testEmptyDatabaseName()
@@ -126,8 +126,8 @@ public function testCommandError()
             'code' => 13,
         ];
 
-        // Using assertArraySubset because newer versions (3.4.7?) also return `codeName`
-        $this->assertArraySubset($expected, $db->command(['listDatabases' => 1]));
+        // Using assertMatches because newer versions (3.4.7?) also return `codeName`
+        $this->assertMatches($expected, $db->command(['listDatabases' => 1]));
     }
 
     public function testCommandCursorTimeout()
@@ -164,7 +164,7 @@ public function testReadPreference()
 
         $this->assertTrue($database->setSlaveOkay(false));
         // Only test a subset since we don't keep tagsets around for RP_PRIMARY
-        $this->assertArraySubset(['type' => \MongoClient::RP_PRIMARY], $database->getReadPreference());
+        $this->assertMatches(['type' => \MongoClient::RP_PRIMARY], $database->getReadPreference());
     }
 
     public function testReadPreferenceIsSetInDriver()
@@ -180,7 +180,6 @@ public function testReadPreferenceIsSetInDriver()
 
         $this->assertSame(ReadPreference::RP_SECONDARY, $readPreference->getMode());
         $this->assertSame([['a' => 'b']], $readPreference->getTagSets());
-
     }
 
     public function testReadPreferenceIsInherited()
@@ -241,6 +240,8 @@ public function testForceError()
 
     public function testExecute()
     {
+        $this->skipTestIf(version_compare($this->getServerVersion(), '4.2.0', '>='), 'Eval no longer works on MongoDB 4.2.0 and newer');
+
         $db = $this->getDatabase();
         $document = ['foo' => 'bar'];
         $this->getCollection()->insert($document);
@@ -291,7 +292,7 @@ public function testGetCollectionInfo()
                         ],
                     ];
                 }
-                $this->assertEquals($expected, $collectionInfo);
+                $this->assertMatches($expected, $collectionInfo);
                 return;
             }
         }
@@ -385,11 +386,13 @@ public function testDropCollection()
             'nIndexesWas' => 1,
             'ok' => 1.0
         ];
-        $this->assertSame($expected, $this->getDatabase()->dropCollection('test'));
+        $this->assertEquals($expected, $this->getDatabase()->dropCollection('test'));
     }
 
     public function testRepair()
     {
+        $this->skipTestIf(version_compare($this->getServerVersion(), '4.2.0', '>='), 'The "repairDatabase" has been removed in MongoDB 4.2.0');
+
         $this->assertSame(['ok' => 1.0], $this->getDatabase()->repair());
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDateTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDateTest.php
index db58c4bb..6f75386b 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDateTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDateTest.php
@@ -17,7 +17,8 @@ public function testTimeZoneDoesNotAlterReturnedDateTime()
         ini_set("date.timezone", "UTC");
 
         // Today at 8h 8m 8s
-        $timestamp = mktime (8, 8, 8); $date = new \MongoDate($timestamp);
+        $timestamp = mktime(8, 8, 8);
+        $date = new \MongoDate($timestamp);
 
         $this->assertSame('08:08:08', $date->toDateTime()->format("H:i:s"));
 
@@ -31,8 +32,8 @@ public function testTimeZoneDoesNotAlterReturnedDateTime()
     public function testCreate()
     {
         $date = new \MongoDate(1234567890, 123456);
-        $this->assertAttributeSame(1234567890, 'sec', $date);
-        $this->assertAttributeSame(123000, 'usec', $date);
+        $this->assertSame(1234567890, $date->sec);
+        $this->assertSame(123000, $date->usec);
 
         $this->assertSame('0.12300000 1234567890', (string) $date);
         $dateTime = $date->toDateTime();
@@ -67,8 +68,8 @@ public function testConvertToBson(\MongoDate $date)
     public function testCreateWithString()
     {
         $date = new \MongoDate('1234567890', '123456');
-        $this->assertAttributeSame(1234567890, 'sec', $date);
-        $this->assertAttributeSame(123000, 'usec', $date);
+        $this->assertSame(1234567890, $date->sec);
+        $this->assertSame(123000, $date->usec);
     }
 
     public function testCreateWithBsonDate()
@@ -78,15 +79,15 @@ public function testCreateWithBsonDate()
         $bsonDate = new \MongoDB\BSON\UTCDateTime(1234567890123);
         $date = new \MongoDate($bsonDate);
 
-        $this->assertAttributeSame(1234567890, 'sec', $date);
-        $this->assertAttributeSame(123000, 'usec', $date);
+        $this->assertSame(1234567890, $date->sec);
+        $this->assertSame(123000, $date->usec);
     }
 
     public function testSupportMillisecondsWithLeadingZeroes()
     {
         $date = new \MongoDate('1234567890', '012345');
-        $this->assertAttributeSame(1234567890, 'sec', $date);
-        $this->assertAttributeSame(12000, 'usec', $date);
+        $this->assertSame(1234567890, $date->sec);
+        $this->assertSame(12000, $date->usec);
 
         $this->assertSame('0.01200000 1234567890', (string) $date);
         $dateTime = $date->toDateTime();
@@ -94,4 +95,33 @@ public function testSupportMillisecondsWithLeadingZeroes()
         $this->assertSame(1234567890, $dateTime->getTimestamp());
         $this->assertSame('012000', $dateTime->format('u'));
     }
+
+    public function testDSTTransitionDoesNotProduceWrongResults()
+    {
+        $initialTZ = ini_get("date.timezone");
+
+        ini_set("date.timezone", "Europe/Madrid");
+
+        $date = new \MongoDate(1603584000);
+        $dateTime = $date->toDateTime();
+
+        $this->assertSame(1603584000, $dateTime->getTimestamp());
+
+        ini_set("date.timezone", $initialTZ);
+    }
+
+    public function testDSTTransitionDoesNotProduceWrongResultsWithMicroSeconds()
+    {
+        $initialTZ = ini_get("date.timezone");
+
+        ini_set("date.timezone", "Europe/Madrid");
+
+        $date = new \MongoDate(1603584000, 123456);
+        $dateTime = $date->toDateTime();
+
+        $this->assertSame(1603584000, $dateTime->getTimestamp());
+        $this->assertSame('123000', $dateTime->format('u'));
+
+        ini_set("date.timezone", $initialTZ);
+    }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDeleteBatchTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDeleteBatchTest.php
index 1e41e31a..6502ae95 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDeleteBatchTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoDeleteBatchTest.php
@@ -9,7 +9,7 @@ class MongoDeleteBatchTest extends TestCase
     public function testSerialize()
     {
         $batch = new \MongoDeleteBatch($this->getCollection());
-        $this->assertInternalType('string', serialize($batch));
+        $this->assertIsString(serialize($batch));
     }
 
     public function testDeleteOne()
@@ -58,6 +58,29 @@ public function testDeleteMany()
         $this->assertSame(0, $newCollection->count());
     }
 
+    public function testDeleteManyWithoutAck()
+    {
+        $collection = $this->getCollection();
+        $batch = new \MongoDeleteBatch($collection);
+
+        $document = ['foo' => 'bar'];
+        $collection->insert($document);
+        unset($document['_id']);
+        $collection->insert($document);
+
+        $this->assertTrue($batch->add(['q' => ['foo' => 'bar'], 'limit' => 0]));
+
+        $expected = [
+            'nRemoved' => 0,
+            'ok' => true,
+        ];
+
+        $this->assertSame($expected, $batch->execute(['w' => 0]));
+
+        $newCollection = $this->getCheckDatabase()->selectCollection('test');
+        $this->assertSame(0, $newCollection->count());
+    }
+
     public function testValidateItem()
     {
         $collection = $this->getCollection();
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSCursorTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSCursorTest.php
index 81c815b4..afbe9c4e 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSCursorTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSCursorTest.php
@@ -3,6 +3,7 @@
 namespace Alcaeus\MongoDbAdapter\Tests\Mongo;
 
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
+use Countable;
 
 class MongoGridFSCursorTest extends TestCase
 {
@@ -13,7 +14,7 @@ public function testSerialize()
         $gridfs->storeBytes('bar', ['filename' => 'bar.txt']);
         $cursor = $gridfs->find(['filename' => 'foo.txt']);
 
-        $this->assertInternalType('string', serialize($cursor));
+        $this->assertIsString(serialize($cursor));
     }
 
     public function testCursorItems()
@@ -25,11 +26,11 @@ public function testCursorItems()
         $cursor = $gridfs->find(['filename' => 'foo.txt']);
         $this->assertCount(1, $cursor);
         foreach ($cursor as $key => $value) {
-            $this->assertSame((string)$id, $key);
+            $this->assertSame((string) $id, $key);
             $this->assertInstanceOf('MongoGridFSFile', $value);
             $this->assertSame('foo', $value->getBytes());
 
-            $this->assertArraySubset([
+            $this->assertMatches([
                 'filename' => 'foo.txt',
                 'chunkSize' => 261120,
                 'length' => 3,
@@ -37,4 +38,16 @@ public function testCursorItems()
             ], $value->file);
         }
     }
+
+    public function testInterfaces()
+    {
+        $this->skipTestIf(extension_loaded('mongo'));
+
+        $gridfs = $this->getGridFS();
+        $id = $gridfs->storeBytes('foo', ['filename' => 'foo.txt']);
+        $gridfs->storeBytes('bar', ['filename' => 'bar.txt']);
+
+        $cursor = $gridfs->find(['filename' => 'foo.txt']);
+        $this->assertInstanceOf(Countable::class, $cursor);
+    }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSFileTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSFileTest.php
index d718b97b..119bf9fd 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSFileTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSFileTest.php
@@ -12,14 +12,14 @@ public function testSerialize()
         $file = $this->getGridFS()->findOne(['filename' => 'foo']);
         $this->assertInstanceOf(\MongoGridFSFile::class, $file);
 
-        $this->assertInternalType('string', serialize($file));
+        $this->assertIsString(serialize($file));
     }
 
     public function testFileProperty()
     {
         $file = $this->getFile();
         $this->assertArrayHasKey('_id', $file->file);
-        $this->assertArraySubset(
+        $this->assertMatches(
             [
                 'length' => 666,
                 'filename' => 'file',
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSTest.php
index 4d163b4f..044ee86c 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSTest.php
@@ -8,7 +8,7 @@ class MongoGridFSTest extends TestCase
 {
     public function testSerialize()
     {
-        $this->assertInternalType('string', serialize($this->getGridFS()));
+        $this->assertIsString(serialize($this->getGridFS()));
     }
 
     public function testChunkProperty()
@@ -70,33 +70,29 @@ public function testStoringData()
 
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $record);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $record->_id);
         $this->assertSame((string) $id, (string) $record->_id);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
-        $this->assertObjectHasAttribute('length', $record);
-        $this->assertAttributeSame(4, 'length', $record);
-        $this->assertObjectHasAttribute('chunkSize', $record);
-        $this->assertAttributeSame(2, 'chunkSize', $record);
-        $this->assertObjectHasAttribute('md5', $record);
-        $this->assertAttributeSame('e2fc714c4727ee9395f324cd2e7f331f', 'md5', $record);
+        $this->assertSame('bar', $record->foo);
+        $this->assertSame(4, $record->length);
+        $this->assertSame(2, $record->chunkSize);
+        $this->assertSame('e2fc714c4727ee9395f324cd2e7f331f', $record->md5);
 
         $chunksCursor = $newChunksCollection->find([], ['sort' => ['n' => 1]]);
         $chunks = iterator_to_array($chunksCursor);
         $firstChunk = $chunks[0];
         $this->assertNotNull($firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', 'files_id', $firstChunk);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $firstChunk->files_id);
         $this->assertSame((string) $id, (string) $firstChunk->files_id);
-        $this->assertAttributeSame(0, 'n', $firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\Binary', 'data', $firstChunk);
+        $this->assertSame(0, $firstChunk->n);
+        $this->assertInstanceOf('MongoDB\BSON\Binary', $firstChunk->data);
         $this->assertSame('ab', (string) $firstChunk->data->getData());
 
         $secondChunck = $chunks[1];
         $this->assertNotNull($secondChunck);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', 'files_id', $secondChunck);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $secondChunck->files_id);
         $this->assertSame((string) $id, (string) $secondChunck->files_id);
-        $this->assertAttributeSame(1, 'n', $secondChunck);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\Binary', 'data', $secondChunck);
+        $this->assertSame(1, $secondChunck->n);
+        $this->assertInstanceOf('MongoDB\BSON\Binary', $secondChunck->data);
         $this->assertSame('cd', (string) $secondChunck->data->getData());
     }
 
@@ -164,29 +160,24 @@ public function testStoreFile()
         $size = filesize($filename);
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $record);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $record->_id);
         $this->assertSame((string) $id, (string) $record->_id);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
-        $this->assertObjectHasAttribute('length', $record);
-        $this->assertAttributeSame($size, 'length', $record);
-        $this->assertObjectHasAttribute('chunkSize', $record);
-        $this->assertAttributeSame(100, 'chunkSize', $record);
-        $this->assertObjectHasAttribute('md5', $record);
-        $this->assertAttributeSame($md5, 'md5', $record);
-        $this->assertObjectHasAttribute('filename', $record);
-        $this->assertAttributeSame($filename, 'filename', $record);
-
-        $numberOfChunks = (int)ceil($size / 100);
+        $this->assertSame('bar', $record->foo);
+        $this->assertSame($size, $record->length);
+        $this->assertSame(100, $record->chunkSize);
+        $this->assertSame($md5, $record->md5);
+        $this->assertSame($filename, $record->filename);
+
+        $numberOfChunks = (int) ceil($size / 100);
         $this->assertSame($numberOfChunks, $newChunksCollection->count());
         $expectedContent = substr(file_get_contents(__FILE__), 0, 100);
 
         $firstChunk = $newChunksCollection->findOne([], ['sort' => ['n' => 1]]);
         $this->assertNotNull($firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', 'files_id', $firstChunk);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $firstChunk->files_id);
         $this->assertSame((string) $id, (string) $firstChunk->files_id);
-        $this->assertAttributeSame(0, 'n', $firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\Binary', 'data', $firstChunk);
+        $this->assertSame(0, $firstChunk->n);
+        $this->assertInstanceOf('MongoDB\BSON\Binary', $firstChunk->data);
         $this->assertSame($expectedContent, (string) $firstChunk->data->getData());
     }
 
@@ -209,29 +200,24 @@ public function testStoreFileResource()
         $filename = basename(__FILE__);
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $record);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $record->_id);
         $this->assertSame((string) $id, (string) $record->_id);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
-        $this->assertObjectHasAttribute('length', $record);
-        $this->assertAttributeSame($size, 'length', $record);
-        $this->assertObjectHasAttribute('chunkSize', $record);
-        $this->assertAttributeSame(100, 'chunkSize', $record);
-        $this->assertObjectHasAttribute('md5', $record);
-        $this->assertAttributeSame($md5, 'md5', $record);
-        $this->assertObjectHasAttribute('filename', $record);
-        $this->assertAttributeSame('test.php', 'filename', $record);
-
-        $numberOfChunks = (int)ceil($size / 100);
+        $this->assertSame('bar', $record->foo);
+        $this->assertSame($size, $record->length);
+        $this->assertSame(100, $record->chunkSize);
+        $this->assertSame($md5, $record->md5);
+        $this->assertSame('test.php', $record->filename);
+
+        $numberOfChunks = (int) ceil($size / 100);
         $this->assertSame($numberOfChunks, $newChunksCollection->count());
         $expectedContent = substr(file_get_contents(__FILE__), 0, 100);
 
         $firstChunk = $newChunksCollection->findOne([], ['sort' => ['n' => 1]]);
         $this->assertNotNull($firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', 'files_id', $firstChunk);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $firstChunk->files_id);
         $this->assertSame((string) $id, (string) $firstChunk->files_id);
-        $this->assertAttributeSame(0, 'n', $firstChunk);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\Binary', 'data', $firstChunk);
+        $this->assertSame(0, $firstChunk->n);
+        $this->assertInstanceOf('MongoDB\BSON\Binary', $firstChunk->data);
         $this->assertSame($expectedContent, (string) $firstChunk->data->getData());
     }
 
@@ -260,20 +246,15 @@ public function testStoreUpload()
         $size = filesize(__FILE__);
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertAttributeInstanceOf('MongoDB\BSON\ObjectID', '_id', $record);
+        $this->assertInstanceOf('MongoDB\BSON\ObjectID', $record->_id);
         $this->assertSame((string) $id, (string) $record->_id);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
-        $this->assertObjectHasAttribute('length', $record);
-        $this->assertAttributeSame($size, 'length', $record);
-        $this->assertObjectHasAttribute('chunkSize', $record);
-        $this->assertAttributeSame(100, 'chunkSize', $record);
-        $this->assertObjectHasAttribute('md5', $record);
-        $this->assertAttributeSame($md5, 'md5', $record);
-        $this->assertObjectHasAttribute('filename', $record);
-        $this->assertAttributeSame('test.php', 'filename', $record);
-
-        $numberOfChunks = (int)ceil($size / 100);
+        $this->assertSame('bar', $record->foo);
+        $this->assertSame($size, $record->length);
+        $this->assertSame(100, $record->chunkSize);
+        $this->assertSame($md5, $record->md5);
+        $this->assertSame('test.php', $record->filename);
+
+        $numberOfChunks = (int) ceil($size / 100);
         $this->assertSame($numberOfChunks, $newChunksCollection->count());
     }
 
@@ -332,7 +313,7 @@ public function testPut()
         $this->assertSame(1, $newCollection->count());
 
         $size = filesize(__FILE__);
-        $numberOfChunks = (int)ceil($size / 100);
+        $numberOfChunks = (int) ceil($size / 100);
         $this->assertSame($numberOfChunks, $newChunksCollection->count());
     }
 
@@ -346,7 +327,7 @@ public function testStoreByteExceptionWhileInsertingRecord()
         $collection->insert($document);
 
         $this->expectException(\MongoGridFSException::class);
-        $this->expectExceptionMessageRegExp('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
+        $this->expectErrorMessageMatches('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
         $this->expectExceptionCode(11000);
 
         $collection->storeBytes('foo', ['_id' => $id]);
@@ -361,7 +342,7 @@ public function testStoreByteExceptionWhileInsertingChunks()
         $collection->chunks->insert($document);
 
         $this->expectException(\MongoGridFSException::class);
-        $this->expectExceptionMessageRegExp('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.chunks/');
+        $this->expectErrorMessageMatches('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.chunks/');
         $this->expectExceptionCode(11000);
 
         $collection->storeBytes('foo');
@@ -376,7 +357,7 @@ public function testStoreFileExceptionWhileInsertingRecord()
         $collection->insert($document);
 
         $this->expectException(\MongoGridFSException::class);
-        $this->expectExceptionMessageRegExp('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
+        $this->expectErrorMessageMatches('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
         $this->expectExceptionCode(11000);
 
         $collection->storeFile(__FILE__, ['_id' => $id]);
@@ -391,7 +372,7 @@ public function testStoreFileExceptionWhileInsertingChunks()
         $collection->chunks->insert($document);
 
         $this->expectException(\MongoGridFSException::class);
-        $this->expectExceptionMessageRegExp('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.chunks/');
+        $this->expectErrorMessageMatches('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.chunks/');
         $this->expectExceptionCode(11000);
 
         $collection->storeFile(__FILE__);
@@ -406,7 +387,7 @@ public function testStoreFileExceptionWhileUpdatingFileRecord()
         $collection->insert($document);
 
         $this->expectException(\MongoGridFSException::class);
-        $this->expectExceptionMessageRegExp('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
+        $this->expectErrorMessageMatches('/Could not store file:.* E11000 duplicate key error .* mongo-php-adapter\.fs\.files/');
         $this->expectExceptionCode(11000);
 
         $collection->storeFile(fopen(__FILE__, 'r'));
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoIdTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoIdTest.php
index 81953bea..1a9bcd32 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoIdTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoIdTest.php
@@ -4,6 +4,7 @@
 
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
 use MongoDB\BSON\ObjectID;
+use ReflectionProperty;
 
 /**
  * @author alcaeus <alcaeus@alcaeus.org>
@@ -40,12 +41,11 @@ public function testCreateWithString()
         $this->assertSame(34335, $id->getPID());
     }
 
-    /**
-     * @expectedException \MongoException
-     * @expectedExceptionMessage Invalid object ID
-     */
     public function testCreateWithInvalidStringThrowsMongoException()
     {
+        $this->expectException('\MongoException');
+        $this->expectExceptionMessage('Invalid object ID');
+
         new \MongoId('invalid');
     }
 
@@ -59,7 +59,7 @@ public function testCreateWithObjectId()
         $id = new \MongoId($objectId);
         $this->assertSame($original, (string) $id);
 
-        $this->assertAttributeNotSame($objectId, 'objectID', $id);
+        $this->assertNotSame($objectId, $this->getAttributeValue($id, 'objectID'));
     }
 
     /**
@@ -83,4 +83,12 @@ public static function dataIsValid()
             'object' => [false, new \stdClass()],
         ];
     }
+
+    private function getAttributeValue(\MongoId $id, $attribute)
+    {
+        $property = new ReflectionProperty($id, $attribute);
+        $property->setAccessible(true);
+
+        return $property->getValue($id);
+    }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoInsertBatchTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoInsertBatchTest.php
index 06a47839..a7badfac 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoInsertBatchTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoInsertBatchTest.php
@@ -9,7 +9,7 @@ class MongoInsertBatchTest extends TestCase
     public function testSerialize()
     {
         $batch = new \MongoInsertBatch($this->getCollection());
-        $this->assertInternalType('string', serialize($batch));
+        $this->assertIsString(serialize($batch));
     }
 
     public function testInsertBatch()
@@ -30,8 +30,28 @@ public function testInsertBatch()
         $this->assertSame(2, $newCollection->count());
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
+        $this->assertSame('bar', $record->foo);
+    }
+
+    public function testInsertBatchWithoutAck()
+    {
+        $batch = new \MongoInsertBatch($this->getCollection());
+
+        $this->assertTrue($batch->add(['foo' => 'bar']));
+        $this->assertTrue($batch->add(['bar' => 'foo']));
+
+        $expected = [
+            'nInserted' => 0,
+            'ok' => true,
+        ];
+
+        $this->assertSame($expected, $batch->execute(['w' => 0]));
+
+        $newCollection = $this->getCheckDatabase()->selectCollection('test');
+        $this->assertSame(2, $newCollection->count());
+        $record = $newCollection->findOne();
+        $this->assertNotNull($record);
+        $this->assertSame('bar', $record->foo);
     }
 
     public function testInsertBatchError()
@@ -60,7 +80,7 @@ public function testInsertBatchError()
         } catch (\MongoWriteConcernException $e) {
             $this->assertSame('Failed write', $e->getMessage());
             $this->assertSame(911, $e->getCode());
-            $this->assertArraySubset($expected, $e->getDocument());
+            $this->assertMatches($expected, $e->getDocument());
         }
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoLogTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoLogTest.php
index daceb6cb..fda63162 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoLogTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoLogTest.php
@@ -8,7 +8,8 @@ class MongoLogTest extends Testcase
 {
     public function testSetCallback()
     {
-        $foo = function() {};
+        $foo = function () {
+        };
         $this->assertTrue(\MongoLog::setCallback($foo));
         $this->assertSame($foo, \MongoLog::getCallback());
     }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoRegexTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoRegexTest.php
index 6ae20d44..a515bbe7 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoRegexTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoRegexTest.php
@@ -13,8 +13,8 @@ class MongoRegexTest extends TestCase
     public function testCreate()
     {
         $regex = new \MongoRegex('/abc/i');
-        $this->assertAttributeSame('abc', 'regex', $regex);
-        $this->assertAttributeSame('i', 'flags', $regex);
+        $this->assertSame('abc', $regex->regex);
+        $this->assertSame('i', $regex->flags);
 
         $this->assertSame('/abc/i', (string) $regex);
 
@@ -41,7 +41,7 @@ public function testCreateWithBsonType()
         $bsonRegex = new \MongoDB\BSON\Regex('abc', 'i');
         $regex = new \MongoRegex($bsonRegex);
 
-        $this->assertAttributeSame('abc', 'regex', $regex);
-        $this->assertAttributeSame('i', 'flags', $regex);
+        $this->assertSame('abc', $regex->regex);
+        $this->assertSame('i', $regex->flags);
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoTimestampTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoTimestampTest.php
index 16c8f2e4..c9d38ea6 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoTimestampTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoTimestampTest.php
@@ -13,8 +13,8 @@ class MongoTimestampTest extends TestCase
     public function testCreate()
     {
         $timestamp = new \MongoTimestamp(1234567890, 987654321);
-        $this->assertAttributeSame(1234567890, 'sec', $timestamp);
-        $this->assertAttributeSame(987654321, 'inc', $timestamp);
+        $this->assertSame(1234567890, $timestamp->sec);
+        $this->assertSame(987654321, $timestamp->inc);
 
         $this->assertSame('1234567890', (string) $timestamp);
 
@@ -38,8 +38,8 @@ public function testCreateWithGlobalInc()
         $timestamp1 = new \MongoTimestamp(1234567890);
         $timestamp2 = new \MongoTimestamp(1234567890);
 
-        $this->assertAttributeSame(0, 'inc', $timestamp1);
-        $this->assertAttributeSame(1, 'inc', $timestamp2);
+        $this->assertSame(0, $timestamp1->inc);
+        $this->assertSame(1, $timestamp2->inc);
     }
 
     public function testCreateWithBsonTimestamp()
@@ -49,8 +49,8 @@ public function testCreateWithBsonTimestamp()
         $bsonTimestamp = new \MongoDB\BSON\Timestamp(987654321, 1234567890);
         $timestamp = new \MongoTimestamp($bsonTimestamp);
 
-        $this->assertAttributeSame(1234567890, 'sec', $timestamp);
-        $this->assertAttributeSame(987654321, 'inc', $timestamp);
+        $this->assertSame(1234567890, $timestamp->sec);
+        $this->assertSame(987654321, $timestamp->inc);
     }
 
     public function testContructorArgumentOrderDiffers()
@@ -63,6 +63,6 @@ public function testContructorArgumentOrderDiffers()
         $bsonTimestamp = new \MongoDB\BSON\Timestamp(12345, 67890);
         $timestamp = new \MongoTimestamp(67890, 12345);
 
-        $this->assertSame((string) $bsonTimestamp, (string)$timestamp->toBSONType());
+        $this->assertSame((string) $bsonTimestamp, (string) $timestamp->toBSONType());
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoUpdateBatchTest.php b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoUpdateBatchTest.php
index 89458dfa..858fe8c7 100644
--- a/tests/Alcaeus/MongoDbAdapter/Mongo/MongoUpdateBatchTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/Mongo/MongoUpdateBatchTest.php
@@ -9,7 +9,7 @@ class MongoUpdateBatchTest extends TestCase
     public function testSerialize()
     {
         $batch = new \MongoUpdateBatch($this->getCollection());
-        $this->assertInternalType('string', serialize($batch));
+        $this->assertIsString(serialize($batch));
     }
 
     public function testUpdateOne()
@@ -35,8 +35,7 @@ public function testUpdateOne()
         $this->assertSame(1, $newCollection->count());
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('foo', 'foo', $record);
+        $this->assertSame('foo', $record->foo);
     }
 
     public function testUpdateOneException()
@@ -71,7 +70,7 @@ public function testUpdateOneException()
         } catch (\MongoWriteConcernException $e) {
             $this->assertSame('Failed write', $e->getMessage());
             $this->assertSame(911, $e->getCode());
-            $this->assertArraySubset($expected, $e->getDocument());
+            $this->assertMatches($expected, $e->getDocument());
         }
     }
 
@@ -100,8 +99,35 @@ public function testUpdateMany()
         $this->assertSame(2, $newCollection->count());
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('foo', 'foo', $record);
+        $this->assertSame('foo', $record->foo);
+    }
+
+    public function testUpdateManyWithoutAck()
+    {
+        $collection = $this->getCollection();
+        $batch = new \MongoUpdateBatch($collection);
+
+        $document = ['foo' => 'bar'];
+        $collection->insert($document);
+        unset($document['_id']);
+        $collection->insert($document);
+
+        $this->assertTrue($batch->add(['q' => ['foo' => 'bar'], 'u' => ['$set' => ['foo' => 'foo']], 'multi' => true]));
+
+        $expected = [
+            'nMatched' => 0,
+            'nModified' => 0,
+            'nUpserted' => 0,
+            'ok' => true,
+        ];
+
+        $this->assertSame($expected, $batch->execute(['w' => 0]));
+
+        $newCollection = $this->getCheckDatabase()->selectCollection('test');
+        $this->assertSame(2, $newCollection->count());
+        $record = $newCollection->findOne();
+        $this->assertNotNull($record);
+        $this->assertSame('foo', $record->foo);
     }
 
     public function testUpdateManyException()
@@ -136,7 +162,7 @@ public function testUpdateManyException()
         } catch (\MongoWriteConcernException $e) {
             $this->assertSame('Failed write', $e->getMessage());
             $this->assertSame(911, $e->getCode());
-            $this->assertArraySubset($expected, $e->getDocument());
+            $this->assertMatches($expected, $e->getDocument());
         }
     }
 
@@ -162,7 +188,7 @@ public function testUpsert()
         ];
 
         $result = $batch->execute();
-        $this->assertArraySubset($expected, $result);
+        $this->assertMatches($expected, $result);
 
         $this->assertInstanceOf('MongoId', $result['upserted'][0]['_id']);
 
@@ -171,8 +197,7 @@ public function testUpsert()
         $this->assertSame(2, $newCollection->count());
         $record = $newCollection->findOne();
         $this->assertNotNull($record);
-        $this->assertObjectHasAttribute('foo', $record);
-        $this->assertAttributeSame('bar', 'foo', $record);
+        $this->assertSame('bar', $record->foo);
     }
 
     public function testValidateItem()
diff --git a/tests/Alcaeus/MongoDbAdapter/TestCase.php b/tests/Alcaeus/MongoDbAdapter/TestCase.php
index 153ad167..1250d1e0 100644
--- a/tests/Alcaeus/MongoDbAdapter/TestCase.php
+++ b/tests/Alcaeus/MongoDbAdapter/TestCase.php
@@ -2,17 +2,29 @@
 
 namespace Alcaeus\MongoDbAdapter\Tests;
 
+use Alcaeus\MongoDbAdapter\Tests\Constraint\Matches;
 use MongoDB\Client;
 use PHPUnit\Framework\TestCase as BaseTestCase;
+use Symfony\Bridge\PhpUnit\SetUpTearDownTrait;
 
 abstract class TestCase extends BaseTestCase
 {
+    use SetUpTearDownTrait;
+
     const INDEX_VERSION_1 = 1;
     const INDEX_VERSION_2 = 2;
 
-    protected function tearDown()
+    private function doTearDown()
     {
         $this->getCheckDatabase()->drop();
+
+        parent::tearDown();
+    }
+
+    public function assertMatches($expected, $value, $message = '')
+    {
+        $constraint = new Matches($expected, true, true, true);
+        $this->assertThat($value, $constraint, $message);
     }
 
     /**
@@ -20,7 +32,7 @@ protected function tearDown()
      */
     protected function getCheckClient()
     {
-        return new Client('mongodb://localhost', ['connect' => true]);
+        return new Client(MONGODB_URI, ['connect' => true]);
     }
 
     /**
@@ -36,7 +48,7 @@ protected function getCheckDatabase()
      * @param array|null $options
      * @return \MongoClient
      */
-    protected function getClient($options = null, $uri = 'mongodb://localhost')
+    protected function getClient($options = null, $uri = MONGODB_URI)
     {
         $args = [$uri];
         if ($options !== null) {
@@ -139,7 +151,7 @@ protected function checkFailPoint()
             /* command not found */
             if ($e->getCode() == 59) {
                 $this->markTestSkipped(
-                  'This test require the mongo daemon to be started with the test flag: --setParameter enableTestCommands=1'
+                    'This test require the mongo daemon to be started with the test flag: --setParameter enableTestCommands=1'
                 );
             }
         }
@@ -153,18 +165,19 @@ protected function failMaxTimeMS()
     /**
      * @param bool $condition
      */
-    protected function skipTestUnless($condition)
+    protected function skipTestUnless($condition, $message = null)
     {
-        $this->skipTestIf(! $condition);
+        $this->skipTestIf(! $condition, $message);
     }
 
     /**
      * @param bool $condition
+     * @param string|null $message
      */
-    protected function skipTestIf($condition)
+    protected function skipTestIf($condition, $message = null)
     {
         if ($condition) {
-            $this->markTestSkipped('Test only applies when running against mongo-php-adapter');
+            $this->markTestSkipped($message !== null ? $message : 'Test only applies when running against mongo-php-adapter');
         }
     }
 
@@ -183,7 +196,11 @@ protected function getServerVersion()
     protected function getFeatureCompatibilityVersion()
     {
         $featureCompatibilityVersion = $this->getClient()->selectDB('admin')->command(['getParameter' => true, 'featureCompatibilityVersion' => true]);
-        return isset($featureCompatibilityVersion['featureCompatibilityVersion']) ? $featureCompatibilityVersion['featureCompatibilityVersion'] : '3.2';
+        if (! isset($featureCompatibilityVersion['featureCompatibilityVersion'])) {
+            return '3.2';
+        }
+
+        return isset($featureCompatibilityVersion['featureCompatibilityVersion']['version']) ? $featureCompatibilityVersion['featureCompatibilityVersion']['version'] : $featureCompatibilityVersion['featureCompatibilityVersion'];
     }
 
     /**
@@ -199,6 +216,6 @@ protected function getDefaultIndexVersion()
 
         // Check featureCompatibilityFlag
         $compatibilityVersion = $this->getFeatureCompatibilityVersion();
-        return $compatibilityVersion === '3.4' ? self::INDEX_VERSION_2 : self::INDEX_VERSION_1;
+        return version_compare($compatibilityVersion, '3.4', '>=') ? self::INDEX_VERSION_2 : self::INDEX_VERSION_1;
     }
 }
diff --git a/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php b/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php
index 635c0c25..7bab4a7c 100644
--- a/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php
+++ b/tests/Alcaeus/MongoDbAdapter/TypeConverterTest.php
@@ -3,7 +3,6 @@
 namespace Alcaeus\MongoDbAdapter\Tests;
 
 use MongoDB\BSON;
-use MongoDB\Driver\Exception;
 use Alcaeus\MongoDbAdapter\TypeConverter;
 use MongoDB\Model\BSONDocument;
 
@@ -38,6 +37,14 @@ public static function converterData()
             'nestedArrays' => [
                 [['foo' => 'bar']], [new BSONDocument(['foo' => 'bar'])]
             ],
+            'dateTime'            => [
+                \DateTime::createFromFormat('Y-m-d\TH:i:sP', '2021-06-30T12:34:56-7'),
+                new BSONDocument([
+                    'date'          => '2021-06-30 12:34:56.000000',
+                    'timezone_type' => 1,
+                    'timezone'      => '-07:00',
+                ]),
+            ],
         ];
     }