diff --git a/includes/MslsMetaBox.php b/includes/MslsMetaBox.php
index bb0396b8..73124c1e 100644
--- a/includes/MslsMetaBox.php
+++ b/includes/MslsMetaBox.php
@@ -273,7 +273,7 @@ public function render_option( int $post_id, ?int $msls_id ): string {
 		return wp_kses(
 			sprintf(
 				'<option value="%d" %s>%s</option>',
-				esc_attr( $post_id ),
+				esc_attr( strval( $post_id ) ),
 				selected( $post_id, $msls_id, false ),
 				get_the_title( $post_id )
 			),
diff --git a/phpunit.xml b/phpunit.xml
index 4882878a..c10c51d2 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -4,8 +4,16 @@
          bootstrap="tests/phpunit/bootstrap.php"
          backupGlobals="true"
          colors="true"
+         testdox="false"
+         displayDetailsOnIncompleteTests="true"
+         displayDetailsOnSkippedTests="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
          displayDetailsOnTestsThatTriggerWarnings="true"
-         cacheDirectory=".phpunit.cache">
+         displayDetailsOnPhpunitDeprecations="true"
+         cacheDirectory=".phpunit.cache"
+>
   <php>
     <const name="MSLS_PLUGIN_PATH" value="multisite-language-switcher/MultisiteLanguageSwitcher.php"/>
     <const name="MSLS_PLUGIN__FILE__" value="/var/www/html/wp-content/plugins/multisite-language-switcher/MultisiteLanguageSwitcher.php"/>
diff --git a/tests/phpunit/ContentImport/TestAttachmentPathFinder.php b/tests/phpunit/ContentImport/TestAttachmentPathFinder.php
index b7824b62..5c5daa25 100644
--- a/tests/phpunit/ContentImport/TestAttachmentPathFinder.php
+++ b/tests/phpunit/ContentImport/TestAttachmentPathFinder.php
@@ -44,4 +44,33 @@ public function test_filter_srcset( $source, $imageSrc, $attachmentId, $expected
 
 		$this->assertEquals( $expected, $this->test->filter_srcset( $source, null, $imageSrc, null, $attachmentId ) );
 	}
+
+	public static function dataprovider_filter_attachement_url(): array {
+		$generic_obj = (object) array( 'guid' => 'http://example.com/image.jpg' );
+
+		$post_mock       = \Mockery::mock( '\WP_Post' );
+		$post_mock->guid = 'http://example.com/image.jpg';
+
+		return array(
+			array( 'http://example.com/image.jpg', $generic_obj, 42 ),
+			array( 'http://example.com/image.jpg', $generic_obj, 0 ),
+			array( 'http://example.com/image.jpg', $post_mock, 42 ),
+		);
+	}
+
+	/**
+	 * @dataProvider dataprovider_filter_attachement_url
+	 */
+	public function test_filter_attachment_url( string $image_src, $source_post, int $attachment_id ): void {
+		$msls_imported = array(
+			'blog' => 1,
+			'post' => 1,
+		);
+
+		Functions\expect( 'get_post_meta' )->zeroOrMoreTimes()->andReturn( $msls_imported );
+		Functions\expect( 'delete_post_meta' )->zeroOrMoreTimes();
+		Functions\expect( 'get_blog_post' )->zeroOrMoreTimes()->andReturn( $source_post );
+
+		$this->assertEquals( $source_post->guid, $this->test->filter_attachment_url( $image_src, $attachment_id ) );
+	}
 }