Fix unit test

See commit 915d8c3 in content-filtering-2 branch.

tests/test-suite.php

@@ -384,7 +384,7 @@ function test_tevkori_filter_content_images() {
 		// Function used to build HTML for the editor.
 		$img = get_image_tag( $id, '', '', '', 'medium' );
 
-		$respimg = preg_replace('/src="([^"]*)/', 'src="$1" ' . $srcset . ' ' . $sizes, $img);
+		$respimg = preg_replace('|<img ([^>]+) />|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img);
 
 		$content = '<p>Welcome to WordPress!  This post contains important information.  After you read it, you can make it private to hide it from visitors but still have the information handy for future reference.</p>
 			<p>First things first:</p>