Index: tests/phpunit/tests/meta.php
===================================================================
--- tests/phpunit/tests/meta.php	(revision 27092)
+++ tests/phpunit/tests/meta.php	(working copy)
@@ -81,8 +81,14 @@
 		$this->assertTrue( metadata_exists( 'user',  $this->author->ID, 'meta_key' ) );
 		$this->assertFalse( metadata_exists( 'user',  1234567890, 'foobarbaz' ) );
 		$this->assertFalse( metadata_exists( 'user',  1234567890, 'meta_key' ) );
-	}
 
+        // Let's see if it returns the correct value when adding a filter.
+        add_filter( 'get_user_metadata', '__return_zero' );
+        $this->assertFalse( metadata_exists( 'user', $this->author->ID, 'meta_key' ) ); // existing meta key
+        $this->assertFalse( metadata_exists( 'user', 1234567890, 'meta_key' ) );
+        remove_filter( 'get_user_metadata', '__return_zero' );
+    }
+
 	/**
 	 * @ticket 18158
 	 */