Drupal\system\Tests\Theme\FastTest does not test anything

Needs a reroll but appears to be dead code maybe?

Rerolled for 10.1.x.

Pretty convinced this is deadcode but will see what the committers say.

The route 'user.autocomplete' was removed in Drupal 8.0.x #2434697: Remove UserAutocompleteController → .

There is another instance of the string 'user/autocomplete'. That should be investigated here as well.

$ git grep 'user.autocomplete' | grep -v drupal[6-7].php
core/modules/node/tests/src/Functional/NodeCreationTest.php:    $this->assertSession()->elementNotExists('xpath', '//input[@id="edit-uid-0-value" and contains(@data-autocomplete-path, "user/autocomplete")]');
core/modules/system/tests/src/Functional/Theme/FastTest.php:    $this->drupalGet('user/autocomplete', ['query' => ['q' => $this->account->getAccountName()]]);

#22 - The other reference to user/autocomplete was removed in 🐛 NodeCreationtest::testAuthorAutocomplete has incorrect selector for falsey check Active

I've created an MR to remove the test. But kind of agree with #17:

What was this originally testing? Should we still test that?

Good question. The test was meant to ensure that the theme registry was not initialized when making a request to the autocomplete route. The theme_test module has an event subscriber that throws a "registry initialized" exception if the theme registry is initialized. This currently only applies to the 'system.entity_autocomplete' route but previously applied to 'user.autocomplete' and 'user.autocomplete_anonymous', before #2434697: Remove UserAutocompleteController → . I'm not sure if there is any test that's checking for that exception, so perhaps that should be removed too? Or we refactor FastTest to use the 'system.entity_autocomplete' route instead.

I did some more digging. We can use 'system.entity_autocomplete' in the test like so:

$this->drupalLogin($this->account);
$selection_settings_key = Crypt::hmacBase64(serialize([]) . 'userdefault', Settings::getHashSalt());;
\Drupal::keyValue('entity_autocomplete')->set($selection_settings_key, []);
$this->drupalGet('/entity_reference_autocomplete/user/default/' . $selection_settings_key, [
  'query' => [
    'q' => $this->account->getAccountName(),
  ],
]);

However we never enter ThemeTestSubscriber::onView so the exception is never thrown anyway.

I think we can just remove the test.

Thanks @mstrelan for digging into that! Agree with your findings.