Enter text in a Drupal TinyMCE WYSIWYG field

gistfile1.txt

  /**
   * Enter text in textareas - this does not text the wysiwg functionality
   *
   * @When /^I enter "([^"]*)" in the "([^"]*)" text field$/
   */
  public function iEnterInTheEditor($text, $field) {

    $page = $this->getMainContext()->getSession()->getPage();

    // Define selectors because the body field is handled differently
    if ($field == 'Body' ) {
      $iframe_selector = '#edit-body-und-0-value_ifr';
    } else {
      $iframe_selector = '#edit-field-' . str_replace(' ', '_', strtolower($field)) . '-und-0-value_ifr';
    }

    // Allow the field to be filled in via Goutte, if the wysiwyg is disabled, or with TinyMCE enabled
    $iframe = $page->find('css', $iframe_selector);
    if(!$iframe) {
      return new When("I fill in \"$field\" with \"$text\"");
    } else {
      $script = "jQuery('iframe$iframe_selector').contents().find('body#tinymce').append('<p>$text</p>')";
      $this->getMainContext()->getSession()->executeScript($script);
    }
  }

I suggest to disable Tiny while testing - you shouldn't test tiny, it's already good tested ;)