code: private function getFixtureRelativeName($fullFixturePath)
      {
          $fixturesPath = FileHelper::normalizePath($this->getFixturePath());
          $fullFixturePath = FileHelper::normalizePath($fullFixturePath);
  
          $relativeName = substr($fullFixturePath, strlen($fixturesPath) + 1);
          $relativeDir = dirname($relativeName) === '.' ? '' : dirname($relativeName) . DIRECTORY_SEPARATOR;
  
          return $relativeDir . basename($fullFixturePath, 'Fixture.php');
      }
docs: Calculates fixture's name
  Basically, strips [[getFixturePath()]] and `Fixture.php' suffix from fixture's full path.
  @see getFixturePath()
  @param string $fullFixturePath Full fixture path
  @return string Relative fixture name