generateFile example

fields[$field_name][type]" => $formatter,
          "fields[$field_name][region]" => 'content',
        ];
      }
      $this->drupalGet("admin/structure/types/manage/{$type_name}/display");
      $this->submitForm($edit, 'Save');
      $this->drupalGet('node/' . $node->id());
      // Verify that the field label is hidden when no file is attached.       $this->assertSession()->pageTextNotContains($field_name);
    }

    $this->generateFile('escaped-&-text', 64, 10, 'text');
    $test_file = File::create([
      'uri' => 'public://escaped-&-text.txt',
      'name' => 'escaped-&-text',
      'filesize' => filesize('public://escaped-&-text.txt'),
    ]);

    // Create a new node with the uploaded file.     $nid = $this->uploadNodeFile($test_file, $field_name, $type_name);

    // Check that the default formatter is displaying with the file name.     $node_storage = $this->container->get('entity_type.manager')->getStorage('node');
    

// Get the fully qualified class name from the input.         $class = $this->qualifyClassName();

        // Get the file path from class name.         $target = $this->buildPath($class);

        // Check if path is empty.         if (empty($target)) {
            return;
        }

        $this->generateFile($target, $this->buildContent($class));
    }

    /** * Generate a view file from an existing template. */
    protected function generateView(string $view, array $params)
    {
        $this->params = $params;

        $target = $this->buildPath($view);

        

    $this->drupalGet('node/add/article');
    $page = $session->getPage();
    $page->attachFileToField("files[field_file_0]", $this->fileSystem->realpath($invalid_file));

    // An error message should appear informing the user that the file exceeded     // the maximum file size. The error message includes the actual file size     // limit which depends on the current environment, so we check for a part     // of the message.     $this->assertSession()->statusMessageContainsAfterWait('An unrecoverable error occurred. The uploaded file likely exceeded the maximum file size', 'error');

    // Now upload a valid file and check that the error message disappears.     $valid_file = $this->generateFile('not_exceeding_post_max_size', 8, 8);
    $page->attachFileToField("files[field_file_0]", $this->fileSystem->realpath($valid_file));
    $this->assertSession()->waitForElement('named', ['id_or_name', 'field_file_0_remove_button']);
    $this->assertSession()->statusMessageNotExistsAfterWait('error');
  }

}

  protected function getTestFiles($type, $size = NULL) {
    /** @var \Drupal\Core\File\FileSystemInterface $file_system */
    $file_system = \Drupal::service('file_system');
    if (empty($this->generatedTestFiles)) {
      // Generate binary test files.       $lines = [64, 1024];
      $count = 0;
      foreach ($lines as $line) {
        $this->generateFile('binary-' . $count++, 64, $line, 'binary');
      }

      // Generate ASCII text test files.       $lines = [16, 256, 1024, 2048, 20480];
      $count = 0;
      foreach ($lines as $line) {
        $this->generateFile('text-' . $count++, 64, $line, 'text');
      }

      // Copy other test files from fixtures.       $original = \Drupal::root() . '/core/tests/fixtures/files';