diff --git a/src/js/_enqueues/admin/common.js b/src/js/_enqueues/admin/common.js
index 3de9447879f5e..b044b722c7a3c 100644
--- a/src/js/_enqueues/admin/common.js
+++ b/src/js/_enqueues/admin/common.js
@@ -1109,11 +1109,46 @@ $( function() {
 			$button.find( '.screen-reader-text' ).text( __( 'Dismiss this notice.' ) );
 			$button.on( 'click.wp-dismiss-notice', function( event ) {
 				event.preventDefault();
-				$el.fadeTo( 100, 0, function() {
-					$el.slideUp( 100, function() {
-						$el.remove();
+
+				var $dismiss_data = { action: 'dismiss-notice' },
+				    $slug = $el.data( 'slug' ),
+				    $expiration = $el.data( 'expiration' );
+
+				if ( ! $slug ) {
+					$el.fadeTo( 100, 0, function() {
+						$el.slideUp( 100, function() {
+							$el.remove();
+						});
 					});
-				});
+				} else {
+					$dismiss_data.slug = $slug;
+
+					if ( $expiration ) {
+						$dismiss_data.expiration = $expiration;
+					}
+
+					$.post(
+						ajaxurl,
+						$dismiss_data
+					).always( function ( response ) {
+						if ( true === response.success ) {
+							$el.fadeTo( 100, 0, function() {
+								$el.slideUp( 100, function() {
+									$el.remove();
+								});
+							});
+						} else {
+							var $noticeDismissalFailed = $( '#notice-dismissal-failed' );
+
+							if ( 0 === $noticeDismissalFailed.length ) {
+								$el.after( '<div id="notice-dismissal-failed" class="notice notice-error"><p>' + response.data + '</p></div>' );
+							} else {
+								$el.after( $noticeDismissalFailed );
+								$noticeDismissalFailed.find( 'p' ).innerHTML = response.data;
+							}
+						}
+					} );
+				}
 			});
 
 			$el.append( $button );
@@ -1733,7 +1768,7 @@ $( function() {
 						setTimeout( function() {
 							var focusIsInToggle  = $.contains( toggleButton, focusedElement );
 							var focusIsInSidebar = $.contains( sidebar, focusedElement );
-							
+
 							if ( ! focusIsInToggle && ! focusIsInSidebar ) {
 								$( toggleButton ).trigger( 'click.wp-responsive' );
 							}
diff --git a/src/wp-admin/admin-ajax.php b/src/wp-admin/admin-ajax.php
index fb191100299ce..0f18c1ebfd172 100644
--- a/src/wp-admin/admin-ajax.php
+++ b/src/wp-admin/admin-ajax.php
@@ -141,6 +141,7 @@
 	'health-check-get-sizes',
 	'toggle-auto-updates',
 	'send-password-reset',
+	'dismiss-notice',
 );
 
 // Deprecated.
diff --git a/src/wp-admin/includes/ajax-actions.php b/src/wp-admin/includes/ajax-actions.php
index 69f5fd469ca94..ef0dbd1d746ed 100644
--- a/src/wp-admin/includes/ajax-actions.php
+++ b/src/wp-admin/includes/ajax-actions.php
@@ -5610,3 +5610,40 @@ function wp_ajax_send_password_reset() {
 		wp_send_json_error( $results->get_error_message() );
 	}
 }
+
+/**
+ * Handles dismissing a notice via AJAX.
+ *
+ * @since 6.5.0
+ */
+function wp_ajax_dismiss_notice() {
+	check_ajax_referer( 'dismiss-notice', 'nonce' );
+
+	if ( ! isset( $_POST['slug'] ) ) {
+		wp_send_json_error( __( 'Failed to dismiss notice: The notice does not have a slug.' ) );
+	}
+
+	$slug = trim( sanitize_text_field( $_POST['slug'] ) );
+	if ( '' === $slug ) {
+		wp_send_json_error( __( "Failed to dismiss notice: The notice's slug must not be an empty string." ) );
+	}
+
+	$expiration = 0;
+	if ( isset( $_POST['expiration'] ) ) {
+		if ( ! is_numeric( $_POST['expiration'] ) ) {
+			wp_send_json_error( __( 'Failed to dismiss notice: The expiration time must be a number of seconds.' ) );
+		}
+
+		$expiration = (int) $_POST['expiration'];
+
+		if ( 0 > $_POST['expiration'] ) {
+			wp_send_json_error( __( 'Failed to dismiss notice: The expiration time must be greater than or equal to 0.' ) );
+		}
+	}
+
+	if ( false === set_site_transient( "wp_admin_notice_dismissed_{$slug}", 1, $expiration ) ) {
+		wp_send_json_error( __( 'Failed to dismiss notice: The notice could not be dismissed.' ) );
+	}
+
+	wp_send_json_success( __( 'The notice was successfully dismissed.' ) );
+}
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index cb490ee1764fa..6449ef8e3a909 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -8756,14 +8756,24 @@ function wp_fuzzy_number_match( $expected, $actual, $precision = 1 ) {
  * @param array  $args {
  *     Optional. An array of arguments for the admin notice. Default empty array.
  *
- *     @type string   $type               Optional. The type of admin notice.
- *                                        For example, 'error', 'success', 'warning', 'info'.
- *                                        Default empty string.
- *     @type bool     $dismissible        Optional. Whether the admin notice is dismissible. Default false.
- *     @type string   $id                 Optional. The value of the admin notice's ID attribute. Default empty string.
- *     @type string[] $additional_classes Optional. A string array of class names. Default empty array.
- *     @type string[] $attributes         Optional. Additional attributes for the notice div. Default empty array.
- *     @type bool     $paragraph_wrap     Optional. Whether to wrap the message in paragraph tags. Default true.
+ *     @type string     $type               Optional. The type of admin notice.
+ *                                          For example, 'error', 'success', 'warning', 'info'.
+ *                                          Default empty string.
+ *     @type bool|array $dismissible        {
+ *         Optional. Whether the admin notice is dismissible. Default false.
+ *
+ *         If false, the notice is not dismissible.
+ *         If true, the notice is dismissible until the next page load.
+ *         If an array, the notice will be dismissed either permanently,
+ *         or until the specified expiration has occurred.
+ *
+ *         @type string $slug       The slug of the notice. Used to store a transient when the notice is dismissed.
+ *         @type int    $expiration Optional. Time until expiration in seconds. Default 0 (no expiration).
+ *     }
+ *     @type string     $id                 Optional. The value of the admin notice's ID attribute. Default empty string.
+ *     @type string[]   $additional_classes Optional. A string array of class names. Default empty array.
+ *     @type string[]   $attributes         Optional. Additional attributes for the notice div. Default empty array.
+ *     @type bool       $paragraph_wrap     Optional. Whether to wrap the message in paragraph tags. Default true.
  * }
  * @return string The markup for an admin notice.
  */
@@ -8822,6 +8832,106 @@ function wp_get_admin_notice( $message, $args = array() ) {
 
 	if ( true === $args['dismissible'] ) {
 		$classes .= ' is-dismissible';
+	} elseif ( is_array( $args['dismissible'] ) ) {
+		// The "slug" key is required.
+		if ( ! isset( $args['dismissible']['slug'] ) || ! is_string( $args['dismissible']['slug'] ) ) {
+			wp_trigger_error(
+				__FUNCTION__,
+				sprintf(
+					/* translators: 1: The "slug" key, 2: The "dismissible" key. */
+					__( 'The "%1$s" key in the "%2$s" array must be a string.' ),
+					'slug',
+					'dismissible'
+				)
+			);
+		} else {
+			$slug = trim( $args['dismissible']['slug'] );
+			if ( '' === $slug ) {
+				wp_trigger_error(
+					__FUNCTION__,
+					sprintf(
+						/* translators: 1: The "slug" key, 2: The "dismissible" key. */
+						__( 'The "%1$s" key in the "%2$s" array must be a non-empty string.' ),
+						'slug',
+						'dismissible'
+					)
+				);
+			} else {
+				// Add a slug data attribute so a transient can be saved when the notice is dismissed.
+				$args['attributes']['data-slug'] = $slug;
+			}
+
+			/*
+			 * If the notice is still dismissed, return early with
+			 * empty notice markup so that nothing can be output.
+			 */
+			if ( 1 === (int) get_site_transient( "wp_admin_notice_dismissed_{$slug}" ) ) {
+				return '';
+			}
+
+			/*
+			 * The "expiration" key is optional.
+			 *
+			 * `isset()` is not used because it will not catch `null` values, which are invalid.
+			 */
+			if ( array_key_exists( 'expiration', $args['dismissible'] ) ) {
+				if ( ! is_int( $args['dismissible']['expiration'] ) ) {
+					/*
+					 * Unset the slug data attribute so that the notice appears on the next page load,
+					 * allowing for corrections to be made without needing to delete the notice's transient.
+					 *
+					 * Without this, the notice would be permanently dismissed.
+					 */
+					unset( $args['attributes']['data-slug'] );
+
+					wp_trigger_error(
+						__FUNCTION__,
+						sprintf(
+							/* translators: 1: The "expiration" key, 2: The "dismissible" key. */
+							__( 'The "%1$s" key in the "%2$s" array must be an integer.' ),
+							'expiration',
+							'dismissible'
+						)
+					);
+				} else {
+					$expiration = (int) $args['dismissible']['expiration'];
+					if ( 0 > $expiration ) {
+						/*
+						 * Unset the slug data attribute so that the notice appears on the next page load,
+						 * allowing for corrections to be made without needing to delete the notice's transient.
+						 *
+						 * Without this, the notice would be permanently dismissed.
+						 */
+						unset( $args['attributes']['data-slug'] );
+
+						wp_trigger_error(
+							__FUNCTION__,
+							sprintf(
+								/* translators: 1: The "expiration" key, 2: The "dismissible" key. */
+								__( 'The "%1$s" key in the "%2$s" array must be greater than or equal to 0.' ),
+								'expiration',
+								'dismissible'
+							)
+						);
+					} else {
+						// Add an expiration data attribute so the notice can be dismissed for a specified duration.
+						$args['attributes']['data-expiration'] = $expiration;
+					}
+				}
+			}
+
+			/*
+			 * By only adding the HTML class when everything is considered valid,
+			 * this means invalid values will result in a notice that cannot be dismissed.
+			 *
+			 * Even if error reporting is disabled for some reason, the developer will know
+			 * immediately that something has gone wrong.
+			 */
+			if ( isset( $args['attributes']['data-slug'] ) ) {
+				$args['attributues']['data-nonce'] = wp_create_nonce( 'dismiss-notice' );
+				$classes                          .= ' is-dismissible';
+			}
+		}
 	}
 
 	if ( is_array( $args['additional_classes'] ) && ! empty( $args['additional_classes'] ) ) {
diff --git a/tests/phpunit/includes/testcase-ajax.php b/tests/phpunit/includes/testcase-ajax.php
index 0478c10900c37..52ea476ac94e4 100644
--- a/tests/phpunit/includes/testcase-ajax.php
+++ b/tests/phpunit/includes/testcase-ajax.php
@@ -113,6 +113,7 @@ abstract class WP_Ajax_UnitTestCase extends WP_UnitTestCase {
 		'get-post-thumbnail-html',
 		'wp-privacy-export-personal-data',
 		'wp-privacy-erase-personal-data',
+		'dismiss-notice',
 	);
 
 	public static function set_up_before_class() {
diff --git a/tests/phpunit/tests/ajax/wpAjaxDismissNotice.php b/tests/phpunit/tests/ajax/wpAjaxDismissNotice.php
new file mode 100644
index 0000000000000..b2edb1b24ec93
--- /dev/null
+++ b/tests/phpunit/tests/ajax/wpAjaxDismissNotice.php
@@ -0,0 +1,412 @@
+<?php
+/**
+ * Admin Ajax functions to be tested.
+ */
+require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
+
+/**
+ * Tests for wp_ajax_dismiss_notice().
+ *
+ * @group ajax
+ *
+ * @covers ::wp_ajax_dismiss_notice
+ */
+class Tests_Ajax_WpAjaxDismissNotice extends WP_Ajax_UnitTestCase {
+
+	/**
+	 * Tests that a notice is dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_dismiss_notice
+	 *
+	 * @param string     $slug       The slug of the notice.
+	 * @param int|string $expiration Time until expiration in seconds. 0 = no expiration (permanent).
+	 *                               'skip' to skip adding the 'expiration' request parameter.
+	 */
+	public function test_should_dismiss_notice( $slug, $expiration ) {
+		// Become an administrator.
+		$this->_setRole( 'administrator' );
+
+		// Set up a default request.
+		$_POST['nonce'] = wp_create_nonce( 'dismiss-notice' );
+		$_POST['slug']  = $slug;
+
+		if ( 'skip' !== $expiration ) {
+			$_POST['expiration'] = $expiration;
+		}
+
+		// Make the request.
+		try {
+			$this->_handleAjax( 'dismiss-notice' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			unset( $e );
+		}
+
+		// Get the response.
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertTrue(
+			$response['success'],
+			'The notice was not dismissed.'
+		);
+
+		$this->assertSame(
+			'The notice was successfully dismissed.',
+			$response['data'],
+			'An unexpected JSON success message was received.'
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_dismiss_notice() {
+		return array(
+			'no expiration provided (should be permanent)' => array(
+				'slug'       => 'mynotice-dismiss-forever-default',
+				'expiration' => 'skip',
+			),
+			'an expiration of 0 seconds (permanent)'       => array(
+				'slug'       => 'mynotice-dismiss-forever-specified',
+				'expiration' => 0,
+			),
+			'an expiration of 30 days'                     => array(
+				'slug'       => 'mynotice-dismiss-for-30-days',
+				'expiration' => 30 * DAY_IN_SECONDS,
+			),
+			'a (bool) true slug' => array(
+				'slug'       => true,
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'an (int) 1 slug' => array(
+				'slug'       => 1,
+				'expiration' => 0,
+			),
+			'an (int) 0 slug' => array(
+				'slug'       => 0,
+				'expiration' => 0,
+			),
+			'a (float) 1.0 slug' => array(
+				'slug'       => 1.0,
+				'expiration' => 0,
+			),
+			'a (float) 0.0 slug' => array(
+				'slug'       => 0.0,
+				'expiration' => 0,
+			),
+			'a NULL "expiration" value' => array(
+				'slug'       => 'mynotice',
+				'expiration' => null,
+			),
+			'a (float) 1.0 "expiration" value' => array(
+				'slug'       => 'mynotice',
+				'expiration' => 1.0,
+			),
+			'a (float) 0.0 "expiration" value' => array(
+				'slug'       => 'mynotice',
+				'expiration' => 0.0,
+			),
+			'a (string) "1" "expiration" value'            => array(
+				'slug'       => 'mynotice',
+				'expiration' => '1',
+			),
+			'a (string) "0" "expiration" value'            => array(
+				'slug'       => 'mynotice',
+				'expiration' => '0',
+			),
+			'a NAN "expiration" value' => array(
+				'slug'       => 'mynotice',
+				'expiration' => NAN,
+			),
+			'an INF "expiration" value' => array(
+				'slug'       => 'mynotice',
+				'expiration' => INF,
+			),
+		);
+	}
+
+	/**
+	 * Tests that a notice with an invalid slug is not dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_not_dismiss_notice_with_invalid_slug
+	 *
+	 * @param mixed      $slug       The slug of the notice.
+	 *                               'skip' to skip adding the 'slug' request parameter.
+	 * @param int|string $expiration Time until expiration in seconds. 0 = no expiration (permanent).
+	 *                               'skip' to skip adding the 'expiration' request parameter.
+	 * @param string     $expected   The expected JSON error.
+	 */
+	public function test_should_not_dismiss_notice_with_invalid_slug( $slug, $expiration, $expected ) {
+		// Become an administrator.
+		$this->_setRole( 'administrator' );
+
+		// Set up a default request.
+		$_POST['nonce'] = wp_create_nonce( 'dismiss-notice' );
+
+		if ( 'skip' !== $slug ) {
+			$_POST['slug'] = $slug;
+		}
+
+		if ( 'skip' !== $expiration ) {
+			$_POST['expiration'] = $expiration;
+		}
+
+		// Make the request.
+		try {
+			$this->_handleAjax( 'dismiss-notice' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			unset( $e );
+		}
+
+		// Get the response.
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertFalse(
+			$response['success'],
+			'The notice was dismissed.'
+		);
+
+		$this->assertSame(
+			$expected,
+			$response['data'],
+			'An unexpected JSON error message was received.'
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_not_dismiss_notice_with_invalid_slug() {
+		return array(
+			'an empty "dismissible" array'                 => array(
+				'slug'       => 'skip',
+				'expiration' => 'skip',
+				'expected'   => 'Failed to dismiss notice: The notice does not have a slug.',
+			),
+			'no "slug" key in the "dismissible" array'     => array(
+				'slug'       => 'skip',
+				'expiration' => 0,
+				'expected'   => 'Failed to dismiss notice: The notice does not have a slug.',
+			),
+			'a NULL "slug" key in the "dismissible" array' => array(
+				'slug'       => null,
+				'expiration' => 0,
+				'expected'   => 'Failed to dismiss notice: The notice does not have a slug.',
+			),
+			'a (bool) false "slug" key in the "dismissible" array' => array(
+				'slug'       => false,
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'an empty array "slug" key in the "dismissible" array' => array(
+				'slug'       => array(),
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'a populated array "slug" key in the "dismissible" array' => array(
+				'slug'       => array( 'mynotice-dismiss-forever' ),
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'an object "slug" key in the "dismissible" array' => array(
+				'slug'       => new stdClass(),
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'an empty string "slug" key in the "dismissible" array' => array(
+				'slug'       => '',
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+			'a "slug" key containing only space in the "dismissible" array' => array(
+				'slug'       => " \r\t\n",
+				'expiration' => 0,
+				'expected'   => "Failed to dismiss notice: The notice's slug must not be an empty string.",
+			),
+		);
+	}
+
+	/**
+	 * Tests that a notice with an invalid slug is not dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_not_dismiss_notice_with_invalid_expiration
+	 *
+	 * @param mixed  $expiration Time until expiration in seconds. 0 = no expiration (permanent).
+	 * @param string $expected   The expected JSON error.
+	 */
+	public function test_should_not_dismiss_notice_with_invalid_expiration( $expiration, $expected ) {
+		// Become an administrator.
+		$this->_setRole( 'administrator' );
+
+		// Set up a default request.
+		$_POST['nonce']      = wp_create_nonce( 'dismiss-notice' );
+		$_POST['slug']       = 'mynotice';
+		$_POST['expiration'] = $expiration;
+
+		// Make the request.
+		try {
+			$this->_handleAjax( 'dismiss-notice' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			unset( $e );
+		}
+
+		// Get the response.
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertFalse(
+			$response['success'],
+			'The notice was dismissed.'
+		);
+
+		$this->assertSame(
+			$expected,
+			$response['data'],
+			'An unexpected JSON error message was received.'
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_not_dismiss_notice_with_invalid_expiration() {
+		return array(
+			'a (bool) false "expiration" value'    => array(
+				'expiration' => false,
+				'expected'   => 'Failed to dismiss notice: The expiration time must be a number of seconds.',
+			),
+			'a (bool) true "expiration" value'     => array(
+				'expiration' => true,
+				'expected'   => 'Failed to dismiss notice: The expiration time must be a number of seconds.',
+			),
+			'an empty array "expiration" value'    => array(
+				'expiration' => array(),
+				'expected'   => 'Failed to dismiss notice: The expiration time must be a number of seconds.',
+			),
+			'a populated array "expiration" value' => array(
+				'expiration' => array( 1 ),
+				'expected'   => 'Failed to dismiss notice: The expiration time must be a number of seconds.',
+			),
+			'an object "expiration" value'         => array(
+				'expiration' => new stdClass(),
+				'expected'   => 'Failed to dismiss notice: The expiration time must be a number of seconds.',
+			),
+			'a (string) "-1" "expiration" value'   => array(
+				'expiration' => '-1',
+				'expected'   => 'Failed to dismiss notice: The expiration time must be greater than or equal to 0.',
+			),
+			'a negative "expiration" value'        => array(
+				'expiration' => -1,
+				'expected'   => 'Failed to dismiss notice: The expiration time must be greater than or equal to 0.',
+			),
+		);
+	}
+
+	/**
+	 * Tests that a notice with an invalid nonce is not dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_not_dismiss_notice_with_invalid_nonce
+	 *
+	 * @param string $nonce The nonce for the request.
+	 *                      'skip' to skip adding the request parameter.
+	 */
+	public function test_should_not_dismiss_notice_with_invalid_nonce( $nonce ) {
+		// Become an administrator.
+		$this->_setRole( 'administrator' );
+
+		// Set up a default request.
+		if ( 'skip' !== $nonce ) {
+			$_POST['nonce'] = $nonce;
+		}
+
+		$_POST['slug']       = 'mynotice';
+		$_POST['expiration'] = 0;
+
+		// Make the request.
+		$this->expectException( 'WPAjaxDieStopException', 'The request did not die.' );
+		$this->expectExceptionMessage( '-1', 'An unexpected exception was thrown.' );
+		$this->_handleAjax( 'dismiss-notice' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_not_dismiss_notice_with_invalid_nonce() {
+		return array(
+			'no nonce'                 => array(
+				'nonce' => 'skip',
+			),
+			'nonce for another action' => array(
+				'nonce' => wp_create_nonce( 'my-other-action' ),
+			),
+		);
+	}
+
+	/**
+	 * Tests that a notice is not dismissed for a non-privileged user.
+	 *
+	 * @ticket
+	 */
+	public function test_should_not_dismiss_notice_for_a_non_privileged_user() {
+		// Set up a default request.
+		$_POST['nonce']      = wp_create_nonce( 'dismiss-notice' );
+		$_POST['slug']       = 'mynotice';
+		$_POST['expiration'] = 0;
+
+		// Make the request.
+		$this->expectException( 'WPAjaxDieContinueException', 'The request did not die and continue.' );
+		$this->expectExceptionMessage( '', 'An unexpected exception was thrown.' );
+		$this->_handleAjax( 'dismiss-notice' );
+	}
+
+	/**
+	 * Tests that a notice is not dismissed that is already dismissed.
+	 *
+	 * @ticket
+	 */
+	public function test_should_not_dismiss_notice_that_is_already_dismissed() {
+		// Dismiss the notice.
+		set_site_transient( 'wp_admin_notice_dismissed_mynotice', 1 );
+
+		// Set up a default request.
+		$_POST['nonce']      = wp_create_nonce( 'dismiss-notice' );
+		$_POST['slug']       = 'mynotice';
+		$_POST['expiration'] = 0;
+
+		// Make the request.
+		try {
+			$this->_handleAjax( 'dismiss-notice' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			unset( $e );
+		}
+
+		// Get the response.
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertFalse(
+			$response['success'],
+			'The notice was dismissed.'
+		);
+
+		$this->assertSame(
+			'Failed to dismiss notice: The notice could not be dismissed.',
+			$response['data'],
+			'An unexpected JSON error message was received.'
+		);
+	}
+}
diff --git a/tests/phpunit/tests/functions/wpAdminNotice.php b/tests/phpunit/tests/functions/wpAdminNotice.php
index fd0ef6c44f2cf..917d3a2603a65 100644
--- a/tests/phpunit/tests/functions/wpAdminNotice.php
+++ b/tests/phpunit/tests/functions/wpAdminNotice.php
@@ -1,326 +1,666 @@
-<?php
-
-/**
- * Tests for `wp_admin_notice()`.
- *
- * @group functions
- *
- * @covers ::wp_admin_notice
- */
-class Tests_Functions_WpAdminNotice extends WP_UnitTestCase {
-
-	/**
-	 * Tests that `wp_admin_notice()` outputs the expected admin notice markup.
-	 *
-	 * @ticket 57791
-	 *
-	 * @dataProvider data_should_output_admin_notice
-	 *
-	 * @param string $message  The message to output.
-	 * @param array  $args     Arguments for the admin notice.
-	 * @param string $expected The expected admin notice markup.
-	 */
-	public function test_should_output_admin_notice( $message, $args, $expected ) {
-		ob_start();
-		wp_admin_notice( $message, $args );
-		$actual = ob_get_clean();
-
-		$this->assertSame( $expected, $actual );
-	}
-
-	/**
-	 * Data provider.
-	 *
-	 * @return array[]
-	 */
-	public function data_should_output_admin_notice() {
-		return array(
-			'defaults'                                  => array(
-				'message'  => 'A notice with defaults.',
-				'args'     => array(),
-				'expected' => '<div class="notice"><p>A notice with defaults.</p></div>',
-			),
-			'an empty message (used for templates)'     => array(
-				'message'  => '',
-				'args'     => array(
-					'type'               => 'error',
-					'dismissible'        => true,
-					'id'                 => 'message',
-					'additional_classes' => array( 'inline', 'hidden' ),
-				),
-				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"><p></p></div>',
-			),
-			'an empty message (used for templates) without paragraph wrapping' => array(
-				'message'  => '',
-				'args'     => array(
-					'type'               => 'error',
-					'dismissible'        => true,
-					'id'                 => 'message',
-					'additional_classes' => array( 'inline', 'hidden' ),
-					'paragraph_wrap'     => false,
-				),
-				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"></div>',
-			),
-			'an "error" notice'                         => array(
-				'message'  => 'An "error" notice.',
-				'args'     => array(
-					'type' => 'error',
-				),
-				'expected' => '<div class="notice notice-error"><p>An "error" notice.</p></div>',
-			),
-			'a "success" notice'                        => array(
-				'message'  => 'A "success" notice.',
-				'args'     => array(
-					'type' => 'success',
-				),
-				'expected' => '<div class="notice notice-success"><p>A "success" notice.</p></div>',
-			),
-			'a "warning" notice'                        => array(
-				'message'  => 'A "warning" notice.',
-				'args'     => array(
-					'type' => 'warning',
-				),
-				'expected' => '<div class="notice notice-warning"><p>A "warning" notice.</p></div>',
-			),
-			'an "info" notice'                          => array(
-				'message'  => 'An "info" notice.',
-				'args'     => array(
-					'type' => 'info',
-				),
-				'expected' => '<div class="notice notice-info"><p>An "info" notice.</p></div>',
-			),
-			'a type that already starts with "notice-"' => array(
-				'message'  => 'A type that already starts with "notice-".',
-				'args'     => array(
-					'type' => 'notice-info',
-				),
-				'expected' => '<div class="notice notice-notice-info"><p>A type that already starts with "notice-".</p></div>',
-			),
-			'a dismissible notice'                      => array(
-				'message'  => 'A dismissible notice.',
-				'args'     => array(
-					'dismissible' => true,
-				),
-				'expected' => '<div class="notice is-dismissible"><p>A dismissible notice.</p></div>',
-			),
-			'no type and an ID'                         => array(
-				'message'  => 'A notice with an ID.',
-				'args'     => array(
-					'id' => 'message',
-				),
-				'expected' => '<div id="message" class="notice"><p>A notice with an ID.</p></div>',
-			),
-			'a type and an ID'                          => array(
-				'message'  => 'A warning notice with an ID.',
-				'args'     => array(
-					'type' => 'warning',
-					'id'   => 'message',
-				),
-				'expected' => '<div id="message" class="notice notice-warning"><p>A warning notice with an ID.</p></div>',
-			),
-			'no type and additional classes'            => array(
-				'message'  => 'A notice with additional classes.',
-				'args'     => array(
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice error notice-alt"><p>A notice with additional classes.</p></div>',
-			),
-			'a type and additional classes'             => array(
-				'message'  => 'A warning notice with additional classes.',
-				'args'     => array(
-					'type'               => 'warning',
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice notice-warning error notice-alt"><p>A warning notice with additional classes.</p></div>',
-			),
-			'a dismissible notice with a type and additional classes' => array(
-				'message'  => 'A dismissible warning notice with a type and additional classes.',
-				'args'     => array(
-					'type'               => 'warning',
-					'dismissible'        => true,
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice notice-warning is-dismissible error notice-alt"><p>A dismissible warning notice with a type and additional classes.</p></div>',
-			),
-			'a notice without paragraph wrapping'       => array(
-				'message'  => '<span>A notice without paragraph wrapping.</span>',
-				'args'     => array(
-					'paragraph_wrap' => false,
-				),
-				'expected' => '<div class="notice"><span>A notice without paragraph wrapping.</span></div>',
-			),
-			'an unsafe type'                            => array(
-				'message'  => 'A notice with an unsafe type.',
-				'args'     => array(
-					'type' => '"><script>alert("Howdy,admin!");</script>',
-				),
-				'expected' => '<div class="notice notice-">alert("Howdy,admin!");"&gt;<p>A notice with an unsafe type.</p></div>',
-			),
-			'an unsafe ID'                              => array(
-				'message'  => 'A notice with an unsafe ID.',
-				'args'     => array(
-					'id' => '"><script>alert( "Howdy, admin!" );</script> <div class="notice',
-				),
-				'expected' => '<div id="">alert( "Howdy, admin!" ); <div class="notice"><p>A notice with an unsafe ID.</p></div>',
-			),
-			'unsafe additional classes'                 => array(
-				'message'  => 'A notice with unsafe additional classes.',
-				'args'     => array(
-					'additional_classes' => array( '"><script>alert( "Howdy, admin!" );</script> <div class="notice' ),
-				),
-				'expected' => '<div class="notice ">alert( "Howdy, admin!" ); <div class="notice"><p>A notice with unsafe additional classes.</p></div>',
-			),
-			'a type that is not a string'               => array(
-				'message'  => 'A notice with a type that is not a string.',
-				'args'     => array(
-					'type' => array(),
-				),
-				'expected' => '<div class="notice"><p>A notice with a type that is not a string.</p></div>',
-			),
-			'a type with only empty space'              => array(
-				'message'  => 'A notice with a type with only empty space.',
-				'args'     => array(
-					'type' => " \t\r\n",
-				),
-				'expected' => '<div class="notice"><p>A notice with a type with only empty space.</p></div>',
-			),
-			'an ID that is not a string'                => array(
-				'message'  => 'A notice with an ID that is not a string.',
-				'args'     => array(
-					'id' => array( 'message' ),
-				),
-				'expected' => '<div class="notice"><p>A notice with an ID that is not a string.</p></div>',
-			),
-			'an ID with only empty space'               => array(
-				'message'  => 'A notice with an ID with only empty space.',
-				'args'     => array(
-					'id' => " \t\r\n",
-				),
-				'expected' => '<div class="notice"><p>A notice with an ID with only empty space.</p></div>',
-			),
-			'dismissible as a truthy value rather than (bool) true' => array(
-				'message'  => 'A notice with dismissible as a truthy value rather than (bool) true.',
-				'args'     => array(
-					'dismissible' => 1,
-				),
-				'expected' => '<div class="notice"><p>A notice with dismissible as a truthy value rather than (bool) true.</p></div>',
-			),
-			'additional classes that are not an array'  => array(
-				'message'  => 'A notice with additional classes that are not an array.',
-				'args'     => array(
-					'additional_classes' => 'class-1 class-2 class-3',
-				),
-				'expected' => '<div class="notice"><p>A notice with additional classes that are not an array.</p></div>',
-			),
-			'additional attribute with a value'         => array(
-				'message'  => 'A notice with an additional attribute with a value.',
-				'args'     => array(
-					'attributes' => array( 'aria-live' => 'assertive' ),
-				),
-				'expected' => '<div class="notice" aria-live="assertive"><p>A notice with an additional attribute with a value.</p></div>',
-			),
-			'additional hidden attribute'               => array(
-				'message'  => 'A notice with the hidden attribute.',
-				'args'     => array(
-					'attributes' => array( 'hidden' => true ),
-				),
-				'expected' => '<div class="notice" hidden><p>A notice with the hidden attribute.</p></div>',
-			),
-			'additional attribute no associative keys'  => array(
-				'message'  => 'A notice with a boolean attribute without an associative key.',
-				'args'     => array(
-					'attributes' => array( 'hidden' ),
-				),
-				'expected' => '<div class="notice" hidden><p>A notice with a boolean attribute without an associative key.</p></div>',
-			),
-			'additional attribute with role'            => array(
-				'message'  => 'A notice with an additional attribute role.',
-				'args'     => array(
-					'attributes' => array( 'role' => 'alert' ),
-				),
-				'expected' => '<div class="notice" role="alert"><p>A notice with an additional attribute role.</p></div>',
-			),
-			'multiple additional attributes'            => array(
-				'message'  => 'A notice with multiple additional attributes.',
-				'args'     => array(
-					'attributes' => array(
-						'role'      => 'alert',
-						'data-test' => -1,
-					),
-				),
-				'expected' => '<div class="notice" role="alert" data-test="-1"><p>A notice with multiple additional attributes.</p></div>',
-			),
-			'data attribute with unsafe value'          => array(
-				'message'  => 'A notice with an additional attribute with an unsafe value.',
-				'args'     => array(
-					'attributes' => array( 'data-unsafe' => '<script>alert( "Howdy, admin!" );</script>' ),
-				),
-				'expected' => '<div class="notice" data-unsafe="&lt;script&gt;alert( &quot;Howdy, admin!&quot; );&lt;/script&gt;"><p>A notice with an additional attribute with an unsafe value.</p></div>',
-			),
-			'additional invalid attribute'              => array(
-				'message'  => 'A notice with an additional attribute that is invalid.',
-				'args'     => array(
-					'attributes' => array( 'not-valid' => 'not-valid' ),
-				),
-				'expected' => '<div class="notice"><p>A notice with an additional attribute that is invalid.</p></div>',
-			),
-			'multiple attributes with "role", invalid, data-*, numeric, and boolean' => array(
-				'message'  => 'A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.',
-				'args'     => array(
-					'attributes' => array(
-						'role'      => 'alert',
-						'disabled'  => 'disabled',
-						'data-name' => 'my-name',
-						'data-id'   => 1,
-						'hidden',
-					),
-				),
-				'expected' => '<div class="notice" role="alert" data-name="my-name" data-id="1" hidden><p>A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.</p></div>',
-			),
-			'paragraph wrapping as a falsy value rather than (bool) false' => array(
-				'message'  => 'A notice with paragraph wrapping as a falsy value rather than (bool) false.',
-				'args'     => array(
-					'paragraph_wrap' => 0,
-				),
-				'expected' => '<div class="notice"><p>A notice with paragraph wrapping as a falsy value rather than (bool) false.</p></div>',
-			),
-		);
-	}
-
-	/**
-	 * Tests that `_doing_it_wrong()` is thrown when a 'type' containing spaces is passed.
-	 *
-	 * @ticket 57791
-	 *
-	 * @expectedIncorrectUsage wp_get_admin_notice
-	 */
-	public function test_should_throw_doing_it_wrong_with_a_type_containing_spaces() {
-		ob_start();
-		wp_admin_notice(
-			'A type containing spaces.',
-			array( 'type' => 'first second third fourth' )
-		);
-		$actual = ob_get_clean();
-
-		$this->assertSame(
-			'<div class="notice notice-first second third fourth"><p>A type containing spaces.</p></div>',
-			$actual
-		);
-	}
-
-	/**
-	 * Tests that `wp_admin_notice()` fires the 'wp_admin_notice' action.
-	 *
-	 * @ticket 57791
-	 */
-	public function test_should_fire_wp_admin_notice_action() {
-		$action = new MockAction();
-		add_action( 'wp_admin_notice', array( $action, 'action' ) );
-
-		ob_start();
-		wp_admin_notice( 'A notice.', array( 'type' => 'success' ) );
-		ob_end_clean();
-
-		$this->assertSame( 1, $action->get_call_count() );
-	}
-}
+<?php
+
+/**
+ * Tests for `wp_admin_notice()`.
+ *
+ * @group functions
+ *
+ * @covers ::wp_admin_notice
+ */
+class Tests_Functions_WpAdminNotice extends WP_UnitTestCase {
+
+	/**
+	 * Tests that `wp_admin_notice()` outputs the expected admin notice markup.
+	 *
+	 * @ticket 57791
+	 *
+	 * @dataProvider data_should_output_admin_notice
+	 *
+	 * @param string $message  The message to output.
+	 * @param array  $args     Arguments for the admin notice.
+	 * @param string $expected The expected admin notice markup.
+	 */
+	public function test_should_output_admin_notice( $message, $args, $expected ) {
+		ob_start();
+		wp_admin_notice( $message, $args );
+		$actual = ob_get_clean();
+
+		$this->assertSame( $expected, $actual );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_output_admin_notice() {
+		return array(
+			'defaults'                                  => array(
+				'message'  => 'A notice with defaults.',
+				'args'     => array(),
+				'expected' => '<div class="notice"><p>A notice with defaults.</p></div>',
+			),
+			'an empty message (used for templates)'     => array(
+				'message'  => '',
+				'args'     => array(
+					'type'               => 'error',
+					'dismissible'        => true,
+					'id'                 => 'message',
+					'additional_classes' => array( 'inline', 'hidden' ),
+				),
+				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"><p></p></div>',
+			),
+			'an empty message (used for templates) without paragraph wrapping' => array(
+				'message'  => '',
+				'args'     => array(
+					'type'               => 'error',
+					'dismissible'        => true,
+					'id'                 => 'message',
+					'additional_classes' => array( 'inline', 'hidden' ),
+					'paragraph_wrap'     => false,
+				),
+				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"></div>',
+			),
+			'an "error" notice'                         => array(
+				'message'  => 'An "error" notice.',
+				'args'     => array(
+					'type' => 'error',
+				),
+				'expected' => '<div class="notice notice-error"><p>An "error" notice.</p></div>',
+			),
+			'a "success" notice'                        => array(
+				'message'  => 'A "success" notice.',
+				'args'     => array(
+					'type' => 'success',
+				),
+				'expected' => '<div class="notice notice-success"><p>A "success" notice.</p></div>',
+			),
+			'a "warning" notice'                        => array(
+				'message'  => 'A "warning" notice.',
+				'args'     => array(
+					'type' => 'warning',
+				),
+				'expected' => '<div class="notice notice-warning"><p>A "warning" notice.</p></div>',
+			),
+			'an "info" notice'                          => array(
+				'message'  => 'An "info" notice.',
+				'args'     => array(
+					'type' => 'info',
+				),
+				'expected' => '<div class="notice notice-info"><p>An "info" notice.</p></div>',
+			),
+			'a type that already starts with "notice-"' => array(
+				'message'  => 'A type that already starts with "notice-".',
+				'args'     => array(
+					'type' => 'notice-info',
+				),
+				'expected' => '<div class="notice notice-notice-info"><p>A type that already starts with "notice-".</p></div>',
+			),
+			'a dismissible notice'                      => array(
+				'message'  => 'A dismissible notice.',
+				'args'     => array(
+					'dismissible' => true,
+				),
+				'expected' => '<div class="notice is-dismissible"><p>A dismissible notice.</p></div>',
+			),
+			'no type and an ID'                         => array(
+				'message'  => 'A notice with an ID.',
+				'args'     => array(
+					'id' => 'message',
+				),
+				'expected' => '<div id="message" class="notice"><p>A notice with an ID.</p></div>',
+			),
+			'a type and an ID'                          => array(
+				'message'  => 'A warning notice with an ID.',
+				'args'     => array(
+					'type' => 'warning',
+					'id'   => 'message',
+				),
+				'expected' => '<div id="message" class="notice notice-warning"><p>A warning notice with an ID.</p></div>',
+			),
+			'no type and additional classes'            => array(
+				'message'  => 'A notice with additional classes.',
+				'args'     => array(
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice error notice-alt"><p>A notice with additional classes.</p></div>',
+			),
+			'a type and additional classes'             => array(
+				'message'  => 'A warning notice with additional classes.',
+				'args'     => array(
+					'type'               => 'warning',
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice notice-warning error notice-alt"><p>A warning notice with additional classes.</p></div>',
+			),
+			'a dismissible notice with a type and additional classes' => array(
+				'message'  => 'A dismissible warning notice with a type and additional classes.',
+				'args'     => array(
+					'type'               => 'warning',
+					'dismissible'        => true,
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice notice-warning is-dismissible error notice-alt"><p>A dismissible warning notice with a type and additional classes.</p></div>',
+			),
+			'a notice without paragraph wrapping'       => array(
+				'message'  => '<span>A notice without paragraph wrapping.</span>',
+				'args'     => array(
+					'paragraph_wrap' => false,
+				),
+				'expected' => '<div class="notice"><span>A notice without paragraph wrapping.</span></div>',
+			),
+			'an unsafe type'                            => array(
+				'message'  => 'A notice with an unsafe type.',
+				'args'     => array(
+					'type' => '"><script>alert("Howdy,admin!");</script>',
+				),
+				'expected' => '<div class="notice notice-">alert("Howdy,admin!");"&gt;<p>A notice with an unsafe type.</p></div>',
+			),
+			'an unsafe ID'                              => array(
+				'message'  => 'A notice with an unsafe ID.',
+				'args'     => array(
+					'id' => '"><script>alert( "Howdy, admin!" );</script> <div class="notice',
+				),
+				'expected' => '<div id="">alert( "Howdy, admin!" ); <div class="notice"><p>A notice with an unsafe ID.</p></div>',
+			),
+			'unsafe additional classes'                 => array(
+				'message'  => 'A notice with unsafe additional classes.',
+				'args'     => array(
+					'additional_classes' => array( '"><script>alert( "Howdy, admin!" );</script> <div class="notice' ),
+				),
+				'expected' => '<div class="notice ">alert( "Howdy, admin!" ); <div class="notice"><p>A notice with unsafe additional classes.</p></div>',
+			),
+			'a type that is not a string'               => array(
+				'message'  => 'A notice with a type that is not a string.',
+				'args'     => array(
+					'type' => array(),
+				),
+				'expected' => '<div class="notice"><p>A notice with a type that is not a string.</p></div>',
+			),
+			'a type with only empty space'              => array(
+				'message'  => 'A notice with a type with only empty space.',
+				'args'     => array(
+					'type' => " \t\r\n",
+				),
+				'expected' => '<div class="notice"><p>A notice with a type with only empty space.</p></div>',
+			),
+			'an ID that is not a string'                => array(
+				'message'  => 'A notice with an ID that is not a string.',
+				'args'     => array(
+					'id' => array( 'message' ),
+				),
+				'expected' => '<div class="notice"><p>A notice with an ID that is not a string.</p></div>',
+			),
+			'an ID with only empty space'               => array(
+				'message'  => 'A notice with an ID with only empty space.',
+				'args'     => array(
+					'id' => " \t\r\n",
+				),
+				'expected' => '<div class="notice"><p>A notice with an ID with only empty space.</p></div>',
+			),
+			'dismissible as a truthy value rather than (bool) true' => array(
+				'message'  => 'A notice with dismissible as a truthy value rather than (bool) true.',
+				'args'     => array(
+					'dismissible' => 1,
+				),
+				'expected' => '<div class="notice"><p>A notice with dismissible as a truthy value rather than (bool) true.</p></div>',
+			),
+			'additional classes that are not an array'  => array(
+				'message'  => 'A notice with additional classes that are not an array.',
+				'args'     => array(
+					'additional_classes' => 'class-1 class-2 class-3',
+				),
+				'expected' => '<div class="notice"><p>A notice with additional classes that are not an array.</p></div>',
+			),
+			'additional attribute with a value'         => array(
+				'message'  => 'A notice with an additional attribute with a value.',
+				'args'     => array(
+					'attributes' => array( 'aria-live' => 'assertive' ),
+				),
+				'expected' => '<div class="notice" aria-live="assertive"><p>A notice with an additional attribute with a value.</p></div>',
+			),
+			'additional hidden attribute'               => array(
+				'message'  => 'A notice with the hidden attribute.',
+				'args'     => array(
+					'attributes' => array( 'hidden' => true ),
+				),
+				'expected' => '<div class="notice" hidden><p>A notice with the hidden attribute.</p></div>',
+			),
+			'additional attribute no associative keys'  => array(
+				'message'  => 'A notice with a boolean attribute without an associative key.',
+				'args'     => array(
+					'attributes' => array( 'hidden' ),
+				),
+				'expected' => '<div class="notice" hidden><p>A notice with a boolean attribute without an associative key.</p></div>',
+			),
+			'additional attribute with role'            => array(
+				'message'  => 'A notice with an additional attribute role.',
+				'args'     => array(
+					'attributes' => array( 'role' => 'alert' ),
+				),
+				'expected' => '<div class="notice" role="alert"><p>A notice with an additional attribute role.</p></div>',
+			),
+			'multiple additional attributes'            => array(
+				'message'  => 'A notice with multiple additional attributes.',
+				'args'     => array(
+					'attributes' => array(
+						'role'      => 'alert',
+						'data-test' => -1,
+					),
+				),
+				'expected' => '<div class="notice" role="alert" data-test="-1"><p>A notice with multiple additional attributes.</p></div>',
+			),
+			'data attribute with unsafe value'          => array(
+				'message'  => 'A notice with an additional attribute with an unsafe value.',
+				'args'     => array(
+					'attributes' => array( 'data-unsafe' => '<script>alert( "Howdy, admin!" );</script>' ),
+				),
+				'expected' => '<div class="notice" data-unsafe="&lt;script&gt;alert( &quot;Howdy, admin!&quot; );&lt;/script&gt;"><p>A notice with an additional attribute with an unsafe value.</p></div>',
+			),
+			'additional invalid attribute'              => array(
+				'message'  => 'A notice with an additional attribute that is invalid.',
+				'args'     => array(
+					'attributes' => array( 'not-valid' => 'not-valid' ),
+				),
+				'expected' => '<div class="notice"><p>A notice with an additional attribute that is invalid.</p></div>',
+			),
+			'multiple attributes with "role", invalid, data-*, numeric, and boolean' => array(
+				'message'  => 'A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.',
+				'args'     => array(
+					'attributes' => array(
+						'role'      => 'alert',
+						'disabled'  => 'disabled',
+						'data-name' => 'my-name',
+						'data-id'   => 1,
+						'hidden',
+					),
+				),
+				'expected' => '<div class="notice" role="alert" data-name="my-name" data-id="1" hidden><p>A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.</p></div>',
+			),
+			'paragraph wrapping as a falsy value rather than (bool) false' => array(
+				'message'  => 'A notice with paragraph wrapping as a falsy value rather than (bool) false.',
+				'args'     => array(
+					'paragraph_wrap' => 0,
+				),
+				'expected' => '<div class="notice"><p>A notice with paragraph wrapping as a falsy value rather than (bool) false.</p></div>',
+			),
+			'a notice that should be dismissed permanently' => array(
+				'message'  => 'A notice that should be dismissed permanently.',
+				'args'     => array(
+					'dismissible' => array(
+						'slug' => 'mynotice-dismiss-permanently',
+					),
+				),
+				'expected' => '<div class="notice is-dismissible" data-slug="mynotice-dismiss-permanently"><p>A notice that should be dismissed permanently.</p></div>',
+			),
+			'a notice that should be dismissed for 30 days' => array(
+				'message'  => 'A notice that should be dismissed for 30 days.',
+				'args'     => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-dismiss-for-30-days',
+						'expiration' => 30 * DAY_IN_SECONDS,
+					),
+				),
+				'expected' => '<div class="notice is-dismissible" data-slug="mynotice-dismiss-for-30-days" data-expiration="2592000"><p>A notice that should be dismissed for 30 days.</p></div>',
+			),
+		);
+	}
+
+	/**
+	 * Tests that `_doing_it_wrong()` is thrown when a 'type' containing spaces is passed.
+	 *
+	 * @ticket 57791
+	 *
+	 * @expectedIncorrectUsage wp_get_admin_notice
+	 */
+	public function test_should_throw_doing_it_wrong_with_a_type_containing_spaces() {
+		ob_start();
+		wp_admin_notice(
+			'A type containing spaces.',
+			array( 'type' => 'first second third fourth' )
+		);
+		$actual = ob_get_clean();
+
+		$this->assertSame(
+			'<div class="notice notice-first second third fourth"><p>A type containing spaces.</p></div>',
+			$actual
+		);
+	}
+
+	/**
+	 * Tests that `wp_admin_notice()` fires the 'wp_admin_notice' action.
+	 *
+	 * @ticket 57791
+	 */
+	public function test_should_fire_wp_admin_notice_action() {
+		$action = new MockAction();
+		add_action( 'wp_admin_notice', array( $action, 'action' ) );
+
+		ob_start();
+		wp_admin_notice( 'A notice.', array( 'type' => 'success' ) );
+		ob_end_clean();
+
+		$this->assertSame( 1, $action->get_call_count() );
+	}
+
+
+	/**
+	 * Tests that `wp_admin_notice()` outputs an empty string for a notice that is still dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_notices_with_dismissible_array
+	 *
+	 * @param array $dismissible The value for the dismissible array.
+	 */
+	public function test_should_output_empty_string_for_a_notice_that_is_still_dismissed( $dismissible ) {
+		// The notice is still dismissed.
+		set_site_transient( 'wp_admin_notice_dismissed_' . $dismissible['slug'], 1 );
+
+		ob_start();
+		wp_admin_notice(
+			'A notice that is still dismissed.',
+			array(
+				'dismissible' => $dismissible,
+			)
+		);
+		$actual = ob_get_clean();
+
+		$this->assertSame( '', $actual );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_notices_with_dismissible_array() {
+		return array(
+			'a permanently dismissed notice (slug only, no expiration provided)' => array(
+				'dismissible' => array(
+					'slug' => 'mynotice-dismiss-forever',
+				),
+			),
+			'a notice dismissed for 30 days' => array(
+				'dismissible' => array(
+					'slug'       => 'mynotice-dismiss-for-30-days',
+					'expiration' => 30 * DAY_IN_SECONDS,
+				),
+			),
+		);
+	}
+
+	/**
+	 * Tests that `wp_admin_notice()` triggers an error.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_trigger_error_for_an_invalid_dismissible_slug
+	 * @dataProvider data_should_trigger_error_for_invalid_dismissible_expiration
+	 *
+	 * @param string $message         The message.
+	 * @param array  $args            Arguments for the admin notice.
+	 * @param string $expected_markup The expected admin notice markup.
+	 * @param string $expected_error  The expected error message.
+	 */
+	public function test_should_trigger_error( $message, $args, $expected_markup, $expected_error ) {
+		// Ensure no previous errors exist.
+		error_clear_last();
+
+		// Backup the error reporting value.
+		$original_error_reporting = error_reporting();
+
+		// Suppress E_USER_NOTICE.
+		error_reporting( E_ALL & ~E_USER_NOTICE );
+
+		ob_start();
+		wp_admin_notice( $message, $args );
+		$actual     = ob_get_clean();
+		$last_error = error_get_last();
+
+		// Reset error reporting.
+		error_reporting( $original_error_reporting );
+
+		$this->assertSame( $expected_markup, $actual );
+		$this->assertIsArray( $last_error, 'An error was not triggered.' );
+		$this->assertSame( E_USER_NOTICE, $last_error['type'], 'The error was not a notice.' );
+		$this->assertSame( $last_error['message'], 'wp_get_admin_notice(): ' . $expected_error, 'The wrong error message was sent.' );
+	}
+
+		/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_trigger_error_for_an_invalid_dismissible_slug() {
+		return array(
+			'an empty "dismissible" array'                 => array(
+				'message'         => 'an empty "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'no "slug" key in the "dismissible" array'     => array(
+				'message'         => 'no "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'expiration' => 30 * DAY_IN_SECONDS ),
+				),
+				'expected_markup' => '<div class="notice"><p>no "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a NULL "slug" key in the "dismissible" array' => array(
+				'message'         => 'a NULL "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => null ),
+				),
+				'expected_markup' => '<div class="notice"><p>a NULL "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a (bool) false "slug" key in the "dismissible" array' => array(
+				'message'         => 'a (bool) false "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => false ),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) false "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a (bool) true "slug" key in the "dismissible" array' => array(
+				'message'         => 'a (bool) true "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => true ),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) true "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an integer "slug" key in the "dismissible" array' => array(
+				'message'         => 'an integer "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => 1234 ),
+				),
+				'expected_markup' => '<div class="notice"><p>an integer "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a float "slug" key in the "dismissible" array' => array(
+				'message'         => 'a float "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => 12.34 ),
+				),
+				'expected_markup' => '<div class="notice"><p>a float "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an empty array "slug" key in the "dismissible" array' => array(
+				'message'         => 'an empty array "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => array() ),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty array "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a populated array "slug" key in the "dismissible" array' => array(
+				'message'         => 'a populated array "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => array( 'mynotice-dismiss-forever' ) ),
+				),
+				'expected_markup' => '<div class="notice"><p>a populated array "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an object "slug" key in the "dismissible" array' => array(
+				'message'         => 'an object "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => new stdClass() ),
+				),
+				'expected_markup' => '<div class="notice"><p>an object "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an empty string "slug" key in the "dismissible" array' => array(
+				'message'         => 'an empty string "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => '' ),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty string "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a non-empty string.',
+			),
+			'a "slug" key containing only space in the "dismissible" array' => array(
+				'message'         => 'a "slug" key containing only space in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => " \r\t\n" ),
+				),
+				'expected_markup' => '<div class="notice"><p>a "slug" key containing only space in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a non-empty string.',
+			),
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_trigger_error_for_invalid_dismissible_expiration() {
+		return array(
+			'a NULL "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a null "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-null-expiration',
+						'expiration' => null,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a null "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a (bool) false "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a (bool) false "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-false-expiration',
+						'expiration' => false,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) false "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a (bool) true "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a (bool) true "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-true-expiration',
+						'expiration' => true,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) true "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an empty array "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an empty array "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-empty-array-expiration',
+						'expiration' => array(),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty array "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a populated array "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a populated array "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-populated-array-expiration',
+						'expiration' => array( 30 * DAY_IN_SECONDS ),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a populated array "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an object "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an object "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-object-expiration',
+						'expiration' => array( 30 * DAY_IN_SECONDS ),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an object "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a float "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a float "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-float-expiration',
+						'expiration' => 30.0,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a float "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a numeric string "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a numeric string "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-numeric-string-expiration',
+						'expiration' => '30',
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a numeric string "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a NAN "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a NAN "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-nan-expiration',
+						'expiration' => NAN,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a NAN "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an INF "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an INF "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-inf-expiration',
+						'expiration' => INF,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an INF "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a negative "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a negative "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-negative-expiration',
+						'expiration' => -1,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a negative "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be greater than or equal to 0.',
+			),
+		);
+	}
+}
diff --git a/tests/phpunit/tests/functions/wpGetAdminNotice.php b/tests/phpunit/tests/functions/wpGetAdminNotice.php
index 2aacdba7fed8d..9cfd4f5739378 100644
--- a/tests/phpunit/tests/functions/wpGetAdminNotice.php
+++ b/tests/phpunit/tests/functions/wpGetAdminNotice.php
@@ -1,326 +1,688 @@
-<?php
-
-/**
- * Tests for `wp_get_admin_notice()`.
- *
- * @group functions
- *
- * @covers ::wp_get_admin_notice
- */
-class Tests_Functions_WpGetAdminNotice extends WP_UnitTestCase {
-
-	/**
-	 * Tests that `wp_get_admin_notice()` returns the expected admin notice markup.
-	 *
-	 * @ticket 57791
-	 *
-	 * @dataProvider data_should_return_admin_notice
-	 *
-	 * @param string $message  The message.
-	 * @param array  $args     Arguments for the admin notice.
-	 * @param string $expected The expected admin notice markup.
-	 */
-	public function test_should_return_admin_notice( $message, $args, $expected ) {
-		$this->assertSame( $expected, wp_get_admin_notice( $message, $args ) );
-	}
-
-	/**
-	 * Data provider.
-	 *
-	 * @return array[]
-	 */
-	public function data_should_return_admin_notice() {
-		return array(
-			'defaults'                                  => array(
-				'message'  => 'A notice with defaults.',
-				'args'     => array(),
-				'expected' => '<div class="notice"><p>A notice with defaults.</p></div>',
-			),
-			'an empty message (used for templates)'     => array(
-				'message'  => '',
-				'args'     => array(
-					'type'               => 'error',
-					'dismissible'        => true,
-					'id'                 => 'message',
-					'additional_classes' => array( 'inline', 'hidden' ),
-				),
-				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"><p></p></div>',
-			),
-			'an empty message (used for templates) without paragraph wrapping' => array(
-				'message'  => '',
-				'args'     => array(
-					'type'               => 'error',
-					'dismissible'        => true,
-					'id'                 => 'message',
-					'additional_classes' => array( 'inline', 'hidden' ),
-					'paragraph_wrap'     => false,
-				),
-				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"></div>',
-			),
-			'an "error" notice'                         => array(
-				'message'  => 'An "error" notice.',
-				'args'     => array(
-					'type' => 'error',
-				),
-				'expected' => '<div class="notice notice-error"><p>An "error" notice.</p></div>',
-			),
-			'a "success" notice'                        => array(
-				'message'  => 'A "success" notice.',
-				'args'     => array(
-					'type' => 'success',
-				),
-				'expected' => '<div class="notice notice-success"><p>A "success" notice.</p></div>',
-			),
-			'a "warning" notice'                        => array(
-				'message'  => 'A "warning" notice.',
-				'args'     => array(
-					'type' => 'warning',
-				),
-				'expected' => '<div class="notice notice-warning"><p>A "warning" notice.</p></div>',
-			),
-			'an "info" notice'                          => array(
-				'message'  => 'An "info" notice.',
-				'args'     => array(
-					'type' => 'info',
-				),
-				'expected' => '<div class="notice notice-info"><p>An "info" notice.</p></div>',
-			),
-			'a type that already starts with "notice-"' => array(
-				'message'  => 'A type that already starts with "notice-".',
-				'args'     => array(
-					'type' => 'notice-info',
-				),
-				'expected' => '<div class="notice notice-notice-info"><p>A type that already starts with "notice-".</p></div>',
-			),
-			'a dismissible notice'                      => array(
-				'message'  => 'A dismissible notice.',
-				'args'     => array(
-					'dismissible' => true,
-				),
-				'expected' => '<div class="notice is-dismissible"><p>A dismissible notice.</p></div>',
-			),
-			'no type and an ID'                         => array(
-				'message'  => 'A notice with an ID.',
-				'args'     => array(
-					'id' => 'message',
-				),
-				'expected' => '<div id="message" class="notice"><p>A notice with an ID.</p></div>',
-			),
-			'a type and an ID'                          => array(
-				'message'  => 'A warning notice with an ID.',
-				'args'     => array(
-					'type' => 'warning',
-					'id'   => 'message',
-				),
-				'expected' => '<div id="message" class="notice notice-warning"><p>A warning notice with an ID.</p></div>',
-			),
-			'no type and additional classes'            => array(
-				'message'  => 'A notice with additional classes.',
-				'args'     => array(
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice error notice-alt"><p>A notice with additional classes.</p></div>',
-			),
-			'a type and additional classes'             => array(
-				'message'  => 'A warning notice with additional classes.',
-				'args'     => array(
-					'type'               => 'warning',
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice notice-warning error notice-alt"><p>A warning notice with additional classes.</p></div>',
-			),
-			'a dismissible notice with a type and additional classes' => array(
-				'message'  => 'A dismissible warning notice with a type and additional classes.',
-				'args'     => array(
-					'type'               => 'warning',
-					'dismissible'        => true,
-					'additional_classes' => array( 'error', 'notice-alt' ),
-				),
-				'expected' => '<div class="notice notice-warning is-dismissible error notice-alt"><p>A dismissible warning notice with a type and additional classes.</p></div>',
-			),
-			'a notice without paragraph wrapping'       => array(
-				'message'  => '<span>A notice without paragraph wrapping.</span>',
-				'args'     => array(
-					'paragraph_wrap' => false,
-				),
-				'expected' => '<div class="notice"><span>A notice without paragraph wrapping.</span></div>',
-			),
-			'an unsafe type'                            => array(
-				'message'  => 'A notice with an unsafe type.',
-				'args'     => array(
-					'type' => '"><script>alert("Howdy,admin!");</script>',
-				),
-				'expected' => '<div class="notice notice-"><script>alert("Howdy,admin!");</script>"><p>A notice with an unsafe type.</p></div>',
-			),
-			'an unsafe ID'                              => array(
-				'message'  => 'A notice with an unsafe ID.',
-				'args'     => array(
-					'id' => '"><script>alert( "Howdy, admin!" );</script> <div class="notice',
-				),
-				'expected' => '<div id=""><script>alert( "Howdy, admin!" );</script> <div class="notice" class="notice"><p>A notice with an unsafe ID.</p></div>',
-			),
-			'unsafe additional classes'                 => array(
-				'message'  => 'A notice with unsafe additional classes.',
-				'args'     => array(
-					'additional_classes' => array( '"><script>alert( "Howdy, admin!" );</script> <div class="notice' ),
-				),
-				'expected' => '<div class="notice "><script>alert( "Howdy, admin!" );</script> <div class="notice"><p>A notice with unsafe additional classes.</p></div>',
-			),
-			'a type that is not a string'               => array(
-				'message'  => 'A notice with a type that is not a string.',
-				'args'     => array(
-					'type' => array(),
-				),
-				'expected' => '<div class="notice"><p>A notice with a type that is not a string.</p></div>',
-			),
-			'a type with only empty space'              => array(
-				'message'  => 'A notice with a type with only empty space.',
-				'args'     => array(
-					'type' => " \t\r\n",
-				),
-				'expected' => '<div class="notice"><p>A notice with a type with only empty space.</p></div>',
-			),
-			'an ID that is not a string'                => array(
-				'message'  => 'A notice with an ID that is not a string.',
-				'args'     => array(
-					'id' => array( 'message' ),
-				),
-				'expected' => '<div class="notice"><p>A notice with an ID that is not a string.</p></div>',
-			),
-			'an ID with only empty space'               => array(
-				'message'  => 'A notice with an ID with only empty space.',
-				'args'     => array(
-					'id' => " \t\r\n",
-				),
-				'expected' => '<div class="notice"><p>A notice with an ID with only empty space.</p></div>',
-			),
-			'dismissible as a truthy value rather than (bool) true' => array(
-				'message'  => 'A notice with dismissible as a truthy value rather than (bool) true.',
-				'args'     => array(
-					'dismissible' => 1,
-				),
-				'expected' => '<div class="notice"><p>A notice with dismissible as a truthy value rather than (bool) true.</p></div>',
-			),
-			'additional classes that are not an array'  => array(
-				'message'  => 'A notice with additional classes that are not an array.',
-				'args'     => array(
-					'additional_classes' => 'class-1 class-2 class-3',
-				),
-				'expected' => '<div class="notice"><p>A notice with additional classes that are not an array.</p></div>',
-			),
-			'additional attribute with a value'         => array(
-				'message'  => 'A notice with an additional attribute with a value.',
-				'args'     => array(
-					'attributes' => array( 'aria-live' => 'assertive' ),
-				),
-				'expected' => '<div class="notice" aria-live="assertive"><p>A notice with an additional attribute with a value.</p></div>',
-			),
-			'additional hidden attribute'               => array(
-				'message'  => 'A notice with the hidden attribute.',
-				'args'     => array(
-					'attributes' => array( 'hidden' => true ),
-				),
-				'expected' => '<div class="notice" hidden><p>A notice with the hidden attribute.</p></div>',
-			),
-			'additional attribute no associative keys'  => array(
-				'message'  => 'A notice with a boolean attribute without an associative key.',
-				'args'     => array(
-					'attributes' => array( 'hidden' ),
-				),
-				'expected' => '<div class="notice" hidden><p>A notice with a boolean attribute without an associative key.</p></div>',
-			),
-			'additional attribute with role'            => array(
-				'message'  => 'A notice with an additional attribute role.',
-				'args'     => array(
-					'attributes' => array( 'role' => 'alert' ),
-				),
-				'expected' => '<div class="notice" role="alert"><p>A notice with an additional attribute role.</p></div>',
-			),
-			'multiple additional attributes'            => array(
-				'message'  => 'A notice with multiple additional attributes.',
-				'args'     => array(
-					'attributes' => array(
-						'role'      => 'alert',
-						'data-test' => -1,
-					),
-				),
-				'expected' => '<div class="notice" role="alert" data-test="-1"><p>A notice with multiple additional attributes.</p></div>',
-			),
-			'data attribute with unsafe value'          => array(
-				'message'  => 'A notice with an additional attribute with an unsafe value.',
-				'args'     => array(
-					'attributes' => array( 'data-unsafe' => '<script>alert( "Howdy, admin!" );</script>' ),
-				),
-				'expected' => '<div class="notice" data-unsafe="&lt;script&gt;alert( &quot;Howdy, admin!&quot; );&lt;/script&gt;"><p>A notice with an additional attribute with an unsafe value.</p></div>',
-			),
-			'multiple attributes with "role", invalid, data-*, numeric, and boolean' => array(
-				'message'  => 'A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.',
-				'args'     => array(
-					'attributes' => array(
-						'role'      => 'alert',
-						'disabled'  => 'disabled',
-						'data-name' => 'my-name',
-						'data-id'   => 1,
-						'hidden',
-					),
-				),
-				'expected' => '<div class="notice" role="alert" disabled="disabled" data-name="my-name" data-id="1" hidden><p>A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.</p></div>',
-			),
-			'paragraph wrapping as a falsy value rather than (bool) false' => array(
-				'message'  => 'A notice with paragraph wrapping as a falsy value rather than (bool) false.',
-				'args'     => array(
-					'paragraph_wrap' => 0,
-				),
-				'expected' => '<div class="notice"><p>A notice with paragraph wrapping as a falsy value rather than (bool) false.</p></div>',
-			),
-		);
-	}
-
-	/**
-	 * Tests that `wp_get_admin_notice()` throws a `_doing_it_wrong()` when
-	 * a 'type' containing spaces is passed.
-	 *
-	 * @ticket 57791
-	 *
-	 * @expectedIncorrectUsage wp_get_admin_notice
-	 */
-	public function test_should_throw_doing_it_wrong_with_a_type_containing_spaces() {
-		$this->assertSame(
-			'<div class="notice notice-first second third fourth"><p>A type containing spaces.</p></div>',
-			wp_get_admin_notice(
-				'A type containing spaces.',
-				array( 'type' => 'first second third fourth' )
-			)
-		);
-	}
-
-	/**
-	 * Tests that `wp_get_admin_notice()` applies filters.
-	 *
-	 * @ticket 57791
-	 *
-	 * @dataProvider data_should_apply_filters
-	 *
-	 * @param string $hook_name The name of the filter hook.
-	 */
-	public function test_should_apply_filters( $hook_name ) {
-		$filter = new MockAction();
-		add_filter( $hook_name, array( $filter, 'filter' ) );
-
-		wp_get_admin_notice( 'A notice.', array( 'type' => 'success' ) );
-
-		$this->assertSame( 1, $filter->get_call_count() );
-	}
-
-	/**
-	 * Data provider.
-	 *
-	 * @return array[]
-	 */
-	public function data_should_apply_filters() {
-		return array(
-			'wp_admin_notice_args'   => array( 'hook_name' => 'wp_admin_notice_args' ),
-			'wp_admin_notice_markup' => array( 'hook_name' => 'wp_admin_notice_markup' ),
-		);
-	}
-}
+<?php
+
+/**
+ * Tests for `wp_get_admin_notice()`.
+ *
+ * @group functions
+ *
+ * @covers ::wp_get_admin_notice
+ */
+class Tests_Functions_WpGetAdminNotice extends WP_UnitTestCase {
+
+	/**
+	 * Tests that `wp_get_admin_notice()` returns the expected admin notice markup.
+	 *
+	 * @ticket 57791
+	 *
+	 * @dataProvider data_should_return_admin_notice
+	 *
+	 * @param string $message  The message.
+	 * @param array  $args     Arguments for the admin notice.
+	 * @param string $expected The expected admin notice markup.
+	 */
+	public function test_should_return_admin_notice( $message, $args, $expected ) {
+		$this->assertSame( $expected, wp_get_admin_notice( $message, $args ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_return_admin_notice() {
+		return array(
+			'defaults'                                  => array(
+				'message'  => 'A notice with defaults.',
+				'args'     => array(),
+				'expected' => '<div class="notice"><p>A notice with defaults.</p></div>',
+			),
+			'an empty message (used for templates)'     => array(
+				'message'  => '',
+				'args'     => array(
+					'type'               => 'error',
+					'dismissible'        => true,
+					'id'                 => 'message',
+					'additional_classes' => array( 'inline', 'hidden' ),
+				),
+				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"><p></p></div>',
+			),
+			'an empty message (used for templates) without paragraph wrapping' => array(
+				'message'  => '',
+				'args'     => array(
+					'type'               => 'error',
+					'dismissible'        => true,
+					'id'                 => 'message',
+					'additional_classes' => array( 'inline', 'hidden' ),
+					'paragraph_wrap'     => false,
+				),
+				'expected' => '<div id="message" class="notice notice-error is-dismissible inline hidden"></div>',
+			),
+			'an "error" notice'                         => array(
+				'message'  => 'An "error" notice.',
+				'args'     => array(
+					'type' => 'error',
+				),
+				'expected' => '<div class="notice notice-error"><p>An "error" notice.</p></div>',
+			),
+			'a "success" notice'                        => array(
+				'message'  => 'A "success" notice.',
+				'args'     => array(
+					'type' => 'success',
+				),
+				'expected' => '<div class="notice notice-success"><p>A "success" notice.</p></div>',
+			),
+			'a "warning" notice'                        => array(
+				'message'  => 'A "warning" notice.',
+				'args'     => array(
+					'type' => 'warning',
+				),
+				'expected' => '<div class="notice notice-warning"><p>A "warning" notice.</p></div>',
+			),
+			'an "info" notice'                          => array(
+				'message'  => 'An "info" notice.',
+				'args'     => array(
+					'type' => 'info',
+				),
+				'expected' => '<div class="notice notice-info"><p>An "info" notice.</p></div>',
+			),
+			'a type that already starts with "notice-"' => array(
+				'message'  => 'A type that already starts with "notice-".',
+				'args'     => array(
+					'type' => 'notice-info',
+				),
+				'expected' => '<div class="notice notice-notice-info"><p>A type that already starts with "notice-".</p></div>',
+			),
+			'a dismissible notice'                      => array(
+				'message'  => 'A dismissible notice.',
+				'args'     => array(
+					'dismissible' => true,
+				),
+				'expected' => '<div class="notice is-dismissible"><p>A dismissible notice.</p></div>',
+			),
+			'no type and an ID'                         => array(
+				'message'  => 'A notice with an ID.',
+				'args'     => array(
+					'id' => 'message',
+				),
+				'expected' => '<div id="message" class="notice"><p>A notice with an ID.</p></div>',
+			),
+			'a type and an ID'                          => array(
+				'message'  => 'A warning notice with an ID.',
+				'args'     => array(
+					'type' => 'warning',
+					'id'   => 'message',
+				),
+				'expected' => '<div id="message" class="notice notice-warning"><p>A warning notice with an ID.</p></div>',
+			),
+			'no type and additional classes'            => array(
+				'message'  => 'A notice with additional classes.',
+				'args'     => array(
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice error notice-alt"><p>A notice with additional classes.</p></div>',
+			),
+			'a type and additional classes'             => array(
+				'message'  => 'A warning notice with additional classes.',
+				'args'     => array(
+					'type'               => 'warning',
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice notice-warning error notice-alt"><p>A warning notice with additional classes.</p></div>',
+			),
+			'a dismissible notice with a type and additional classes' => array(
+				'message'  => 'A dismissible warning notice with a type and additional classes.',
+				'args'     => array(
+					'type'               => 'warning',
+					'dismissible'        => true,
+					'additional_classes' => array( 'error', 'notice-alt' ),
+				),
+				'expected' => '<div class="notice notice-warning is-dismissible error notice-alt"><p>A dismissible warning notice with a type and additional classes.</p></div>',
+			),
+			'a notice without paragraph wrapping'       => array(
+				'message'  => '<span>A notice without paragraph wrapping.</span>',
+				'args'     => array(
+					'paragraph_wrap' => false,
+				),
+				'expected' => '<div class="notice"><span>A notice without paragraph wrapping.</span></div>',
+			),
+			'an unsafe type'                            => array(
+				'message'  => 'A notice with an unsafe type.',
+				'args'     => array(
+					'type' => '"><script>alert("Howdy,admin!");</script>',
+				),
+				'expected' => '<div class="notice notice-"><script>alert("Howdy,admin!");</script>"><p>A notice with an unsafe type.</p></div>',
+			),
+			'an unsafe ID'                              => array(
+				'message'  => 'A notice with an unsafe ID.',
+				'args'     => array(
+					'id' => '"><script>alert( "Howdy, admin!" );</script> <div class="notice',
+				),
+				'expected' => '<div id=""><script>alert( "Howdy, admin!" );</script> <div class="notice" class="notice"><p>A notice with an unsafe ID.</p></div>',
+			),
+			'unsafe additional classes'                 => array(
+				'message'  => 'A notice with unsafe additional classes.',
+				'args'     => array(
+					'additional_classes' => array( '"><script>alert( "Howdy, admin!" );</script> <div class="notice' ),
+				),
+				'expected' => '<div class="notice "><script>alert( "Howdy, admin!" );</script> <div class="notice"><p>A notice with unsafe additional classes.</p></div>',
+			),
+			'a type that is not a string'               => array(
+				'message'  => 'A notice with a type that is not a string.',
+				'args'     => array(
+					'type' => array(),
+				),
+				'expected' => '<div class="notice"><p>A notice with a type that is not a string.</p></div>',
+			),
+			'a type with only empty space'              => array(
+				'message'  => 'A notice with a type with only empty space.',
+				'args'     => array(
+					'type' => " \t\r\n",
+				),
+				'expected' => '<div class="notice"><p>A notice with a type with only empty space.</p></div>',
+			),
+			'an ID that is not a string'                => array(
+				'message'  => 'A notice with an ID that is not a string.',
+				'args'     => array(
+					'id' => array( 'message' ),
+				),
+				'expected' => '<div class="notice"><p>A notice with an ID that is not a string.</p></div>',
+			),
+			'an ID with only empty space'               => array(
+				'message'  => 'A notice with an ID with only empty space.',
+				'args'     => array(
+					'id' => " \t\r\n",
+				),
+				'expected' => '<div class="notice"><p>A notice with an ID with only empty space.</p></div>',
+			),
+			'dismissible as a truthy value rather than (bool) true' => array(
+				'message'  => 'A notice with dismissible as a truthy value rather than (bool) true.',
+				'args'     => array(
+					'dismissible' => 1,
+				),
+				'expected' => '<div class="notice"><p>A notice with dismissible as a truthy value rather than (bool) true.</p></div>',
+			),
+			'additional classes that are not an array'  => array(
+				'message'  => 'A notice with additional classes that are not an array.',
+				'args'     => array(
+					'additional_classes' => 'class-1 class-2 class-3',
+				),
+				'expected' => '<div class="notice"><p>A notice with additional classes that are not an array.</p></div>',
+			),
+			'additional attribute with a value'         => array(
+				'message'  => 'A notice with an additional attribute with a value.',
+				'args'     => array(
+					'attributes' => array( 'aria-live' => 'assertive' ),
+				),
+				'expected' => '<div class="notice" aria-live="assertive"><p>A notice with an additional attribute with a value.</p></div>',
+			),
+			'additional hidden attribute'               => array(
+				'message'  => 'A notice with the hidden attribute.',
+				'args'     => array(
+					'attributes' => array( 'hidden' => true ),
+				),
+				'expected' => '<div class="notice" hidden><p>A notice with the hidden attribute.</p></div>',
+			),
+			'additional attribute no associative keys'  => array(
+				'message'  => 'A notice with a boolean attribute without an associative key.',
+				'args'     => array(
+					'attributes' => array( 'hidden' ),
+				),
+				'expected' => '<div class="notice" hidden><p>A notice with a boolean attribute without an associative key.</p></div>',
+			),
+			'additional attribute with role'            => array(
+				'message'  => 'A notice with an additional attribute role.',
+				'args'     => array(
+					'attributes' => array( 'role' => 'alert' ),
+				),
+				'expected' => '<div class="notice" role="alert"><p>A notice with an additional attribute role.</p></div>',
+			),
+			'multiple additional attributes'            => array(
+				'message'  => 'A notice with multiple additional attributes.',
+				'args'     => array(
+					'attributes' => array(
+						'role'      => 'alert',
+						'data-test' => -1,
+					),
+				),
+				'expected' => '<div class="notice" role="alert" data-test="-1"><p>A notice with multiple additional attributes.</p></div>',
+			),
+			'data attribute with unsafe value'          => array(
+				'message'  => 'A notice with an additional attribute with an unsafe value.',
+				'args'     => array(
+					'attributes' => array( 'data-unsafe' => '<script>alert( "Howdy, admin!" );</script>' ),
+				),
+				'expected' => '<div class="notice" data-unsafe="&lt;script&gt;alert( &quot;Howdy, admin!&quot; );&lt;/script&gt;"><p>A notice with an additional attribute with an unsafe value.</p></div>',
+			),
+			'multiple attributes with "role", invalid, data-*, numeric, and boolean' => array(
+				'message'  => 'A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.',
+				'args'     => array(
+					'attributes' => array(
+						'role'      => 'alert',
+						'disabled'  => 'disabled',
+						'data-name' => 'my-name',
+						'data-id'   => 1,
+						'hidden',
+					),
+				),
+				'expected' => '<div class="notice" role="alert" disabled="disabled" data-name="my-name" data-id="1" hidden><p>A notice with multiple attributes with "role", invalid, "data-*", numeric, and boolean.</p></div>',
+			),
+			'paragraph wrapping as a falsy value rather than (bool) false' => array(
+				'message'  => 'A notice with paragraph wrapping as a falsy value rather than (bool) false.',
+				'args'     => array(
+					'paragraph_wrap' => 0,
+				),
+				'expected' => '<div class="notice"><p>A notice with paragraph wrapping as a falsy value rather than (bool) false.</p></div>',
+			),
+			'a notice that should be dismissed permanently' => array(
+				'message'  => 'A notice that should be dismissed permanently.',
+				'args'     => array(
+					'dismissible' => array(
+						'slug' => 'mynotice-dismiss-permanently',
+					),
+				),
+				'expected' => '<div class="notice is-dismissible" data-slug="mynotice-dismiss-permanently"><p>A notice that should be dismissed permanently.</p></div>',
+			),
+			'a notice that should be dismissed for 30 days' => array(
+				'message'  => 'A notice that should be dismissed for 30 days.',
+				'args'     => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-dismiss-for-30-days',
+						'expiration' => 30 * DAY_IN_SECONDS,
+					),
+				),
+				'expected' => '<div class="notice is-dismissible" data-slug="mynotice-dismiss-for-30-days" data-expiration="2592000"><p>A notice that should be dismissed for 30 days.</p></div>',
+			),
+		);
+	}
+
+	/**
+	 * Tests that `wp_get_admin_notice()` throws a `_doing_it_wrong()` when
+	 * a 'type' containing spaces is passed.
+	 *
+	 * @ticket 57791
+	 *
+	 * @expectedIncorrectUsage wp_get_admin_notice
+	 */
+	public function test_should_throw_doing_it_wrong_with_a_type_containing_spaces() {
+		$this->assertSame(
+			'<div class="notice notice-first second third fourth"><p>A type containing spaces.</p></div>',
+			wp_get_admin_notice(
+				'A type containing spaces.',
+				array( 'type' => 'first second third fourth' )
+			)
+		);
+	}
+
+	/**
+	 * Tests that `wp_get_admin_notice()` applies filters.
+	 *
+	 * @ticket 57791
+	 *
+	 * @dataProvider data_should_apply_filters
+	 *
+	 * @param string $hook_name The name of the filter hook.
+	 */
+	public function test_should_apply_filters( $hook_name ) {
+		$filter = new MockAction();
+		add_filter( $hook_name, array( $filter, 'filter' ) );
+
+		wp_get_admin_notice( 'A notice.', array( 'type' => 'success' ) );
+
+		$this->assertSame( 1, $filter->get_call_count() );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_apply_filters() {
+		return array(
+			'wp_admin_notice_args'   => array( 'hook_name' => 'wp_admin_notice_args' ),
+			'wp_admin_notice_markup' => array( 'hook_name' => 'wp_admin_notice_markup' ),
+		);
+	}
+
+	/**
+	 * Tests that `wp_get_admin_notice()` returns an empty string for a notice that is still dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_notices_with_dismissible_array
+	 *
+	 * @param array $dismissible The value for the dismissible array.
+	 */
+	public function test_should_return_empty_string_for_a_notice_that_is_still_dismissed( $dismissible ) {
+		// The notice is still dismissed.
+		set_site_transient( 'wp_admin_notice_dismissed_' . $dismissible['slug'], 1 );
+
+		$this->assertSame(
+			'',
+			wp_get_admin_notice(
+				'A notice that is still dismissed.',
+				array(
+					'dismissible' => $dismissible,
+				)
+			)
+		);
+	}
+
+	/**
+	 * Tests that `wp_get_admin_notice()` does not apply markup filters for a notice that is still dismissed.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_notices_with_dismissible_array
+	 *
+	 * @param array $dismissible The value for the dismissible array.
+	 */
+	public function test_should_not_apply_markup_filters_for_a_notice_that_is_still_dismissed( $dismissible ) {
+		$filter = new MockAction();
+		add_filter( 'wp_admin_notice_markup', array( $filter, 'filter' ) );
+
+		// The notice is still dismissed.
+		set_site_transient( 'wp_admin_notice_dismissed_' . $dismissible['slug'], 1 );
+
+		wp_get_admin_notice(
+			'A notice that is still dismissed.',
+			array(
+				'dismissible' => $dismissible,
+			)
+		);
+
+		$this->assertSame( 0, $filter->get_call_count() );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_notices_with_dismissible_array() {
+		return array(
+			'a permanently dismissed notice (slug only, no expiration provided)' => array(
+				'dismissible' => array(
+					'slug' => 'mynotice-dismiss-forever',
+				),
+			),
+			'a notice dismissed for 30 days' => array(
+				'dismissible' => array(
+					'slug'       => 'mynotice-dismiss-for-30-days',
+					'expiration' => 30 * DAY_IN_SECONDS,
+				),
+			),
+		);
+	}
+
+	/**
+	 * Tests that `wp_get_admin_notice()` triggers an error.
+	 *
+	 * @ticket
+	 *
+	 * @dataProvider data_should_trigger_error_for_an_invalid_dismissible_slug
+	 * @dataProvider data_should_trigger_error_for_invalid_dismissible_expiration
+	 *
+	 * @param string $message         The message.
+	 * @param array  $args            Arguments for the admin notice.
+	 * @param string $expected_markup The expected admin notice markup.
+	 * @param string $expected_error  The expected error message.
+	 */
+	public function test_should_trigger_error( $message, $args, $expected_markup, $expected_error ) {
+		// Ensure no previous errors exist.
+		error_clear_last();
+
+		// Backup the error reporting value.
+		$original_error_reporting = error_reporting();
+
+		// Suppress E_USER_NOTICE.
+		error_reporting( E_ALL & ~E_USER_NOTICE );
+
+		$actual     = wp_get_admin_notice( $message, $args );
+		$last_error = error_get_last();
+
+		// Reset error reporting.
+		error_reporting( $original_error_reporting );
+
+		$this->assertSame( $expected_markup, $actual );
+		$this->assertIsArray( $last_error, 'An error was not triggered.' );
+		$this->assertSame( E_USER_NOTICE, $last_error['type'], 'The error was not a notice.' );
+		$this->assertSame( $last_error['message'], 'wp_get_admin_notice(): ' . $expected_error, 'The wrong error message was sent.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_trigger_error_for_an_invalid_dismissible_slug() {
+		return array(
+			'an empty "dismissible" array'                 => array(
+				'message'         => 'an empty "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'no "slug" key in the "dismissible" array'     => array(
+				'message'         => 'no "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'expiration' => 30 * DAY_IN_SECONDS ),
+				),
+				'expected_markup' => '<div class="notice"><p>no "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a NULL "slug" key in the "dismissible" array' => array(
+				'message'         => 'a NULL "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => null ),
+				),
+				'expected_markup' => '<div class="notice"><p>a NULL "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a (bool) false "slug" key in the "dismissible" array' => array(
+				'message'         => 'a (bool) false "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => false ),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) false "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a (bool) true "slug" key in the "dismissible" array' => array(
+				'message'         => 'a (bool) true "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => true ),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) true "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an integer "slug" key in the "dismissible" array' => array(
+				'message'         => 'an integer "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => 1234 ),
+				),
+				'expected_markup' => '<div class="notice"><p>an integer "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a float "slug" key in the "dismissible" array' => array(
+				'message'         => 'a float "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => 12.34 ),
+				),
+				'expected_markup' => '<div class="notice"><p>a float "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an empty array "slug" key in the "dismissible" array' => array(
+				'message'         => 'an empty array "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => array() ),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty array "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'a populated array "slug" key in the "dismissible" array' => array(
+				'message'         => 'a populated array "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => array( 'mynotice-dismiss-forever' ) ),
+				),
+				'expected_markup' => '<div class="notice"><p>a populated array "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an object "slug" key in the "dismissible" array' => array(
+				'message'         => 'an object "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => new stdClass() ),
+				),
+				'expected_markup' => '<div class="notice"><p>an object "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a string.',
+			),
+			'an empty string "slug" key in the "dismissible" array' => array(
+				'message'         => 'an empty string "slug" key in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => '' ),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty string "slug" key in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a non-empty string.',
+			),
+			'a "slug" key containing only space in the "dismissible" array' => array(
+				'message'         => 'a "slug" key containing only space in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array( 'slug' => " \r\t\n" ),
+				),
+				'expected_markup' => '<div class="notice"><p>a "slug" key containing only space in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "slug" key in the "dismissible" array must be a non-empty string.',
+			),
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_should_trigger_error_for_invalid_dismissible_expiration() {
+		return array(
+			'a NULL "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a null "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-null-expiration',
+						'expiration' => null,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a null "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a (bool) false "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a (bool) false "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-false-expiration',
+						'expiration' => false,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) false "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a (bool) true "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a (bool) true "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-true-expiration',
+						'expiration' => true,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a (bool) true "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an empty array "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an empty array "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-empty-array-expiration',
+						'expiration' => array(),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an empty array "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a populated array "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a populated array "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-populated-array-expiration',
+						'expiration' => array( 30 * DAY_IN_SECONDS ),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a populated array "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an object "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an object "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-object-expiration',
+						'expiration' => array( 30 * DAY_IN_SECONDS ),
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an object "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a float "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a float "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-float-expiration',
+						'expiration' => 30.0,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a float "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a numeric string "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a numeric string "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-numeric-string-expiration',
+						'expiration' => '30',
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a numeric string "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a NAN "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a NAN "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-nan-expiration',
+						'expiration' => NAN,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a NAN "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'an INF "expiration" value in the "dismissible" array' => array(
+				'message'         => 'an INF "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-inf-expiration',
+						'expiration' => INF,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>an INF "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be an integer.',
+			),
+			'a negative "expiration" value in the "dismissible" array' => array(
+				'message'         => 'a negative "expiration" value in the "dismissible" array',
+				'args'            => array(
+					'dismissible' => array(
+						'slug'       => 'mynotice-negative-expiration',
+						'expiration' => -1,
+					),
+				),
+				'expected_markup' => '<div class="notice"><p>a negative "expiration" value in the "dismissible" array</p></div>',
+				'expected_error'  => 'The "expiration" key in the "dismissible" array must be greater than or equal to 0.',
+			),
+		);
+	}
+}