I have two tests files with tests that need to shadow the t() function in the Node Revision Delete project, one test file is placed in:


And the other in:


At this time I shadow the t() function with the same code at the end of each test file because the t() function is needed to run tests in both files.

namespace Drupal\node_revision_delete\Utility;

 * Shadow t() system call.
 * @param string $string
 *   A string containing the English text to translate.
 * @return string
 *   The translated string.
function t($string) {
  return $string;

When I run each test file all is working fine, but when I run all the project tests I get an error as I have declared the t() function twice:

PHP Fatal error: Cannot redeclare Drupal\node_revision_delete\Utility\t() (previously declared in /Users/adriancid/Sites/drupal84-test/modules/drupal.org/node_revision_delete/tests/src/Unit/NodeRevisionDeleteTest.php:357) in /Users/adriancid/Sites/drupal84-test/modules/drupal.org/node_revision_delete/tests/src/Unit/Utility/TimeTest.php on line 195

The only way that I found to make these works is to pass the tests that need the t() function from one test file to the other, but doing this I will have a mix of tests from diferent classes and I won't be able to use the @covers section in the test definition.

So, what is the correct way to shadow a core function used in two different tests files?

1 Answer 1


Wrap it in a !function_exists()

See core/tests/Drupal/Tests/Core/Render/Element/MachineNameTest.php for example:


namespace Drupal\Core\Render\Element;

if (!function_exists('t')) {

  function t($string, array $args = []) {
    return strtr($string, $args);


That said, t() as a specific example is deprecated and should not be used in classes, use the StringTranslationTrait/service instead and you can actually inject it.

  • Hi @Berdir, thanks for your answer, I use the t() function because it is used in a static method in a Utility function. I tried your solution but it doesn't work, can you check the patch here? drupal.org/project/node_revision_delete/issues/… Aug 8, 2018 at 14:15
  • Its weird, the test works on drupal.org but not in my local environment, I'm still getting the same error. Aug 8, 2018 at 15:39
  • 1
    drupal.org runs tests through run-tests.sh, which spawns a separate process for each test. Sounds like your utility classs then maybe shouldn't be static because you have dependencies to services? unit-testability is one of the reasons you want to create services and use DI instead of static methods. You're fixing the wrong problem :)
    – Berdir
    Aug 8, 2018 at 18:11
  • I don't have dependencies on services, you can check the code at cgit.drupalcode.org/node_revision_delete/tree/src/Utility/… I posted a question related to Utility class and Services on drupal.stackexchange.com/q/251111/28275 and it seems that I can keep my method as static, I don't know what do you think about this. Aug 8, 2018 at 18:34
  • Yes, you do. t() is just a wrapper around creating a new TranslatableMarkup() object, which in turn uses the string_translation service. You have dependencies, they're just hidden behind a function.
    – Berdir
    Aug 8, 2018 at 20:29

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