def METHOD_NAME():
    """
    Verify that authenticate(...) returns the expected result for input that does not
    meet the enforced constraints. Note that this test does not actually validate tokens.
    """
    dummy_kfp_endpoint = "https://localhost:8888"
    dummy_runtime_config_name = "bearer_runtime_config"
    # valid token values are strings that are not None, empty, or comprise of whitespaces only
    for invalid_token in [None, "", "   "]:
        with pytest.raises(AuthenticationError) as exc_error:
            ExistingBearerTokenAuthenticator().authenticate(
                dummy_kfp_endpoint, dummy_runtime_config_name, invalid_token
            )
        assert exc_error.value._provider == SupportedAuthProviders.EXISTING_BEARER_TOKEN
        assert "A token/password is required to perform this type of authentication." in exc_error.value._message
        assert f"Update runtime configuration '{dummy_runtime_config_name}'" in exc_error.value._message