@Test
public void persist() {

    final Cognito cognito = new Cognito(TOKEN, IDENTITY_ID, EXPIRES_AT);
    localCognitoTokenStore.persist(cognito);
    assertEquals(cognito, localCognitoTokenStore.getCognitoToken());
    localCognitoTokenStore.persist(null);
    assertEquals(null, localCognitoTokenStore.getCognitoToken());
}