@Test
public void nullCredentialsAreCreatedForTesting() throws Exception {

  configuration.setBoolean(getConfigKey(ENABLE_SERVICE_ACCOUNTS_SUFFIX), false);
  configuration.setBoolean(getConfigKey(ENABLE_NULL_CREDENTIAL_SUFFIX), true);
  CredentialFactory credentialFactory = getCredentialFactory();
  assertThat(credentialFactory.getCredential(TEST_SCOPES)).isNull();
}