captcha_set_form_id_setting() or forms are broken

All tests that set a captcha to a form seems no longer working. All tests are failing.

Example:

    // Enable 'captcha/Math' CAPTCHA on login form.
    captcha_set_form_id_setting('user_login_form', 'captcha/Math');

    $this->drupalGet('user/login');
    $this->assertNoRaw($grecaptcha, '[testReCaptchaOnLoginForm]: reCAPTCHA is not shown on form.');