diff --git a/composer.json b/composer.json
index 0acae13..1e1b096 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
   "type": "library",
   "require": {
     "php": ">=7.0",
-    "phpunit/phpunit": "^6.0"
+    "phpunit/phpunit": "^6.0|^7.0"
   },
   "license": "BSD-3-Clause",
   "authors": [
diff --git a/src/Git.php b/src/Git.php
index 833a77a..7e83fd1 100644
--- a/src/Git.php
+++ b/src/Git.php
@@ -11,7 +11,7 @@
 
 class Git implements VCS
 {
-    private $binary = '/usr/bin/git';
+    private $binary = 'git';
 
     public function __construct($binary = "")
     {
@@ -24,7 +24,7 @@ public function __construct($binary = "")
         }
 
         if ($this->gitExists() !== true) {
-            throw new GitException("Git doesn't appear to exist in: " . $this->binary);
+            throw new GitException($this->binary . " doesn't appear to exist in: " . $this->binary);
         }
 
         if ($this->isProjectGit() !== true) {
@@ -43,18 +43,12 @@ private function isOSWindows(): bool
 
     public function gitExists(): bool
     {
-        $returnVar = intval(trim(shell_exec($this->binary . " &> /dev/null; echo $?")));
-
-        if ($returnVar === 1) {
-            return true;
-        }
-
-        return false;
+        return !empty('which ' . $this->binary);
     }
 
     private function isProjectGit(): bool
     {
-        $isProjectGit = trim(shell_exec("git rev-parse --is-inside-work-tree"));
+        $isProjectGit = trim(shell_exec($this->binary . " rev-parse --is-inside-work-tree"));
 
         if ($isProjectGit === "true") {
             return true;
@@ -65,14 +59,15 @@ private function isProjectGit(): bool
 
     public function getChangedFiles(): array
     {
-
-        $changes = $this->execute("git diff --name-only");
+        $arguments = $_SERVER['argv'];
+        
+        $from = isset($arguments[1]) ? $arguments[1] : 'HEAD^';
+        $to = isset($arguments[2]) ? $arguments[2] : 'HEAD';
+        
+        $changes = $this->execute($this->binary . " diff --name-only");
         $changes .= PHP_EOL;
-
-        if ($this->countCommits() > 1) {
-            $changes .= $this->execute("git diff --name-only HEAD^ HEAD");
-        }
-
+        $changes .= $this->execute($this->binary . " diff --name-only $from $to");
+        
         $changes = trim($changes);
         $files = explode(PHP_EOL, $changes);
         return $files;
@@ -80,7 +75,7 @@ public function getChangedFiles(): array
 
     private function countCommits(): int
     {
-        return intval(trim($this->execute("git shortlog | grep -E '^[ ]+\\w+' | wc -l")));
+        return intval(trim($this->execute($this->binary . " shortlog | grep -E '^[ ]+\\w+' | wc -l")));
     }
 
     private function execute(string $command): string
@@ -88,4 +83,4 @@ private function execute(string $command): string
         return trim(shell_exec($command));
     }
 
-}
\ No newline at end of file
+}
diff --git a/src/WhatsChanged.php b/src/WhatsChanged.php
index 933face..253f7af 100644
--- a/src/WhatsChanged.php
+++ b/src/WhatsChanged.php
@@ -22,25 +22,16 @@ public function testChanges()
     {
         $changes = $this->VCS->getChangedFiles();
         $testFiles = $this->getTestFiles($changes);
-
-        $mask = "%-30s %-30s\n";
-
-        $fails = array();
-
-        foreach ($testFiles as $file) {
-            $exec = exec("./vendor/bin/phpunit " . $file, $full);
-
-            if (strpos($exec, 'OK ') !== false) {
-                printf($mask, $file, $exec);
-            } else {
-                printf($mask, $file, 'FAIL - '.$exec);
-                array_push($fails, implode(PHP_EOL, $full));
-            }
-        }
-
-        if (!empty($fails)) {
-            echo PHP_EOL.PHP_EOL."FAILED TEST OUTPUTS:".PHP_EOL.PHP_EOL.implode(" ", $fails).PHP_EOL.PHP_EOL;
+        
+        if(empty($testFiles)) {
+            die('No tests to run' . PHP_EOL);
         }
+        
+        $regex = '(' . str_replace(['tests/', '/', '.php'], ['', '\\\\', ''], implode('|', $testFiles)) . ')';
+        
+        $exec = system("./vendor/bin/phpunit --filter '" . $regex . "'", $code);
+        
+        exit($code);
     }
 
     public function getTestFiles(array $changes): array
@@ -112,4 +103,4 @@ private function turnIntoTestFile(string $file): string
         return $newFile;
 
     }
-}
\ No newline at end of file
+}