oops, THIS test does use the regular mock fixture - so should be 19

tests/src/FunctionalJavascript/ProjectBrowserUiTestJsonApi.php

@@ -504,7 +504,7 @@ class ProjectBrowserUiTestJsonApi extends WebDriverTestBase {
     // Verify that only Drupal.org mockapi plugin is enabled.
     $this->drupalGet('admin/modules/browse');
     $this->svelteInitHelper('css', '.pb-filter__categories input[type="checkbox"]');
-    $assert_session->elementsCount('css', '.pb-filter__categories input[type="checkbox"]', 54);
+    $assert_session->elementsCount('css', '.pb-filter__categories input[type="checkbox"]', 19);
   }
 
 }