Tests adding a text editor to an existing text format.
function testAddEditorToExistingFormat() {
$this
->enableUnicornEditor();
$this
->drupalLogin($this->admin_user);
$this
->drupalGet('admin/config/content/formats/filtered_html');
$edit = $this
->selectUnicornEditor();
// Configure Unicorn Editor's setting to another value.
$edit['editor[settings][foo]'] = 'baz';
$this
->drupalPost(NULL, $edit, t('Save configuration'));
$this
->verifyUnicornEditorConfiguration('filtered_html', 'baz');
}