@Test
public void getReasonOfFailureFromSuccessfulInstance() {

    final AuthenticationResult underTest =
            DefaultAuthenticationResult.successful(dittoHeaders, authorizationContext);
    assertThatExceptionOfType(IllegalStateException.class)
            .isThrownBy(underTest::getReasonOfFailure)
            .withMessage("Authentication was successful!")
            .withNoCause();
}