Android testing create methods just for testing

Issue

I'm trying to build a test for activity with JUnit and espresso.

But I faced a problem. my activity depending on a previous activity which was supposed to load user data from a database.

I store the user data in a private variable (to prevent any unwanted changes) and the only way to apply a value to it, is to use a loadFromDatabase method.

But I can't use this method while testing, because it has a callback listener (it sends a request to a server) and I need to load this data immediately in order to load the activity

public User {
    private static User mCurrentUser = ...;

    public static void loadFromDatabase() { ... }
}


public MainActivityTest {

   public MainActivityTest() {
       // load the data                   
       User.loadFromDatabase({
          // on complete callback
       })

       // load the activity
       activity = new ActivityTestRule(MainActivity.class)
   }

}

public MainActivity extends Activity {

  public void onCreate() {
      // needs the user data
      User.mCurrentUser...
  }

}

How can I handle this kind of problem without making mCurrentUser public?

Is there a way to create methods in the regular classes just for testing?

Thanks.

Solution

You can mock it. For mocking you can use mocking libraries like Mockito & PowerMockito.

Create a method in User to return the value and mock that method. If you want this method exclusively for testing then mark it with @VisibleForTesting to restrict access to it. eg;

public class User{
  private static User mCurrentUser;
  public static User getCurrentUser(){
    return mCurrentUser;
  }
}


    @RunWith(PowerMockRunner.class)
    @PrepareForTest(User.class)
    public MainActivityTest{
       @Test
       public void testCurrentUser{
        User probableUserDataFromDB = Mockito.mock(User.class); // Create a   mock instance of User class with some expected behaviour for testing purpose

        Mockito.when(probableUserDataFromDB.getUserName).thenReturn("my unique name");
        PowerMockito.mockstatic(User.class); // Readying the static methods for mocking
    Mockito.when(User.getCurrentUser).thenReturn(probableUserDataFromDB);// mock static method and return a mocked user instance with some expected behaviour

 //continue with your test.................
}

Also read about pros & cons :).

Answered By - NIPHIN