How to ignore error of $this->drupalGet

I've the following test:

$this->drupalGet('node');
$this->assertNoResponse(200, t('User is redirected to the Authorization page.'));

And during some SSO validation, user is redirected to external website for authorization which in this point the test should pass (from the point of test).
But what is happening, it throws the error:

GET https://xxx/x/x/x/AuthenticationWeb/getCookieAccessKeyAndLogin.do?flurl=http%3A%2F%2Fx%2Fx returned 0 (0 bytes).

no matter which Assert I'll set after that.
Is there any way to ignore the error result of $this->drupalGet, no matter what? Or eventually force it to redirect (based on HTTPS and invalid certificate)?
Adding @ in the front doesn't help.