diff --git a/src/wp-includes/l10n.php b/src/wp-includes/l10n.php
index 0c6b75ea24..72a74ff0ac 100644
--- a/src/wp-includes/l10n.php
+++ b/src/wp-includes/l10n.php
@@ -1040,7 +1040,7 @@ function load_script_textdomain( $handle, $domain = 'default', $path = null ) {
 	// If the host is the same or it's a relative URL.
 	if (
 		( ! isset( $content_url['path'] ) || strpos( $src_url['path'], $content_url['path'] ) === 0 ) &&
-		( ! isset( $src_url['host'] ) || $src_url['host'] === $content_url['host'] )
+		( ! isset( $src_url['host'] ) || ! isset( $content_url['host'] ) || $src_url['host'] === $content_url['host'] )
 	) {
 		// Make the src relative the specific plugin or theme.
 		if ( isset( $content_url['path'] ) ) {
@@ -1057,7 +1057,7 @@ function load_script_textdomain( $handle, $domain = 'default', $path = null ) {
 		$relative = implode( '/', $relative );
 	} elseif (
 		( ! isset( $plugins_url['path'] ) || strpos( $src_url['path'], $plugins_url['path'] ) === 0 ) &&
-		( ! isset( $src_url['host'] ) || $src_url['host'] === $plugins_url['host'] )
+		( ! isset( $src_url['host'] ) || ! isset( $plugins_url['host'] ) || $src_url['host'] === $plugins_url['host'] )
 	) {
 		// Make the src relative the specific plugin.
 		if ( isset( $plugins_url['path'] ) ) {
@@ -1072,7 +1072,7 @@ function load_script_textdomain( $handle, $domain = 'default', $path = null ) {
 
 		$relative = array_slice( $relative, 1 ); // Remove <plugin name>.
 		$relative = implode( '/', $relative );
-	} elseif ( ! isset( $src_url['host'] ) || $src_url['host'] === $site_url['host'] ) {
+	} elseif ( ! isset( $src_url['host'] ) || ! isset( $site_url['host'] ) || $src_url['host'] === $site_url['host'] ) {
 		if ( ! isset( $site_url['path'] ) ) {
 			$relative = trim( $src_url['path'], '/' );
 		} elseif ( ( strpos( $src_url['path'], trailingslashit( $site_url['path'] ) ) === 0 ) ) {
diff --git a/tests/phpunit/tests/l10n/loadScriptTextdomain.php b/tests/phpunit/tests/l10n/loadScriptTextdomain.php
index 9f4e1012ba..457f529c61 100644
--- a/tests/phpunit/tests/l10n/loadScriptTextdomain.php
+++ b/tests/phpunit/tests/l10n/loadScriptTextdomain.php
@@ -5,8 +5,121 @@
  * @group i18n
  */
 class Tests_L10n_loadScriptTextdomain extends WP_UnitTestCase {
-	public function site_url_subdirectory( $site_url ) {
-		return $site_url . '/wp';
+
+	/**
+	 * @ticket 45528
+	 * @ticket 46336
+	 * @ticket 46387
+	 * @ticket 49145
+	 *
+	 * @dataProvider data_test_resolve_relative_path
+	 */
+	public function test_resolve_relative_path( $translation_path, $handle, $src, $textdomain, $filter = array() ) {
+		if ( ! empty( $filter ) ) {
+			add_filter( $filter[0], $filter[1], 10, isset( $filter[2] ) ? $filter[2] : 1 );
+		}
+		wp_enqueue_script( $handle, $src, array(), null );
+
+		$expected = file_get_contents( DIR_TESTDATA . $translation_path );
+		$this->assertSame( $expected, load_script_textdomain( $handle, $textdomain, DIR_TESTDATA . '/languages' ) );
+	}
+
+	public function data_test_resolve_relative_path() {
+		return array(
+			// @ticket 45528
+			array(
+				'/languages/en_US-813e104eb47e13dd4cc5af844c618754.json',
+				'test-example-root',
+				'/wp-includes/js/script.js',
+				'default',
+			),
+			// Assets on a CDN.
+			array(
+				'/languages/en_US-813e104eb47e13dd4cc5af844c618754.json',
+				'test-example-cdn',
+				'https://my-cdn.com/wordpress/wp-includes/js/script.js',
+				'default',
+				array( 'load_script_textdomain_relative_path', array( $this, 'relative_path_from_cdn' ), 2 ),
+			),
+			// Test for WordPress installs in a subdirectory.
+			array(
+				'/languages/en_US-813e104eb47e13dd4cc5af844c618754.json',
+				'test-example-subdir',
+				'/wp/wp-includes/js/script.js',
+				'default',
+				array(
+					'site_url',
+					function ( $site_url ) {
+						return $site_url . '/wp';
+					},
+				),
+			),
+			// @ticket 46336
+			array(
+				'/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json',
+				'plugin-example-1',
+				'https://plugins.example.com/my-plugin/js/script.js',
+				'internationalized-plugin',
+				array(
+					'plugins_url',
+					function () {
+						return 'https://plugins.example.com';
+					},
+				),
+			),
+			// @ticket 46387
+			array(
+				'/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json',
+				'plugin-example-2',
+				'https://content.example.com/plugins/my-plugin/js/script.js',
+				'internationalized-plugin',
+				array(
+					'content_url',
+					function () {
+						return 'https://content.example.com';
+					},
+				),
+			),
+			// @ticket 49145
+			array(
+				'/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json',
+				'test-when-no-content_url-host',
+				'https://content.example.com/plugins/my-plugin/js/script.js',
+				'internationalized-plugin',
+				array(
+					'content_url',
+					function () {
+						return '/';
+					},
+				),
+			),
+			// @ticket 49145
+			array(
+				'/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json',
+				'test-when-no-plugins_url-host',
+				'https://plugins.example.com/my-plugin/js/script.js',
+				'internationalized-plugin',
+				array(
+					'plugins_url',
+					function () {
+						return '/';
+					},
+				),
+			),
+			// @ticket 49145
+			array(
+				'/languages/en_US-813e104eb47e13dd4cc5af844c618754.json',
+				'test-when-no-site_url-host',
+				'/wp/wp-includes/js/script.js',
+				'default',
+				array(
+					'site_url',
+					function () {
+						return '/wp';
+					},
+				),
+			),
+		);
 	}
 
 	public function relative_path_from_cdn( $relative, $src ) {
@@ -16,58 +129,4 @@ class Tests_L10n_loadScriptTextdomain extends WP_UnitTestCase {
 
 		return $relative;
 	}
-
-	public function plugins_url_custom_domain() {
-		return 'https://plugins.example.com';
-	}
-
-	public function content_url_custom_domain_with_no_path() {
-		return 'https://content.example.com';
-	}
-
-	/**
-	 * @ticket 45528
-	 */
-	public function test_resolve_relative_path() {
-		$json_translations = file_get_contents( DIR_TESTDATA . '/languages/en_US-813e104eb47e13dd4cc5af844c618754.json' );
-
-		wp_enqueue_script( 'test-example-root', '/wp-includes/js/script.js', array(), null );
-		$this->assertSame( $json_translations, load_script_textdomain( 'test-example-root', 'default', DIR_TESTDATA . '/languages' ) );
-
-		// Assets on a CDN.
-		add_filter( 'load_script_textdomain_relative_path', array( $this, 'relative_path_from_cdn' ), 10, 2 );
-		wp_enqueue_script( 'test-example-cdn', 'https://my-cdn.com/wordpress/wp-includes/js/script.js', array(), null );
-		$this->assertSame( $json_translations, load_script_textdomain( 'test-example-cdn', 'default', DIR_TESTDATA . '/languages' ) );
-		remove_filter( 'load_script_textdomain_relative_path', array( $this, 'relative_path_from_cdn' ) );
-
-		// Test for WordPress installs in a subdirectory.
-		add_filter( 'site_url', array( $this, 'site_url_subdirectory' ) );
-		wp_enqueue_script( 'test-example-subdir', '/wp/wp-includes/js/script.js', array(), null );
-		$this->assertSame( $json_translations, load_script_textdomain( 'test-example-subdir', 'default', DIR_TESTDATA . '/languages' ) );
-		remove_filter( 'site_url', array( $this, 'site_url_subdirectory' ) );
-	}
-
-	/**
-	 * @ticket 46336
-	 */
-	public function test_resolve_relative_path_custom_plugins_url() {
-		$json_translations = file_get_contents( DIR_TESTDATA . '/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json' );
-
-		add_filter( 'plugins_url', array( $this, 'plugins_url_custom_domain' ) );
-		wp_enqueue_script( 'plugin-example-1', 'https://plugins.example.com/my-plugin/js/script.js', array(), null );
-		$this->assertSame( $json_translations, load_script_textdomain( 'plugin-example-1', 'internationalized-plugin', DIR_TESTDATA . '/languages' ) );
-		remove_filter( 'plugins_url', array( $this, 'plugins_url_custom_domain' ) );
-	}
-
-	/**
-	 * @ticket 46387
-	 */
-	public function test_resolve_relative_path_custom_content_url() {
-		$json_translations = file_get_contents( DIR_TESTDATA . '/languages/plugins/internationalized-plugin-en_US-2f86cb96a0233e7cb3b6f03ad573be0b.json' );
-
-		add_filter( 'content_url', array( $this, 'content_url_custom_domain_with_no_path' ) );
-		wp_enqueue_script( 'plugin-example-2', 'https://content.example.com/plugins/my-plugin/js/script.js', array(), null );
-		$this->assertSame( $json_translations, load_script_textdomain( 'plugin-example-2', 'internationalized-plugin', DIR_TESTDATA . '/languages' ) );
-		remove_filter( 'content_url', array( $this, 'content_url_custom_domain_with_no_path' ) );
-	}
 }