Robolectric buildActivity() with Mockito spy?

Robolectric buildActivity() with Mockito Spy

In Android development, testing is crucial for ensuring the quality and reliability of your applications. Robolectric is a popular testing framework that allows you to run Android tests without the need for an emulator or device. Mockito is another widely used mocking framework that simplifies the creation of mock objects for unit testing. This article will delve into the powerful combination of Robolectric’s buildActivity() method and Mockito spies to facilitate robust Android testing.

Understanding the Concept

Robolectric’s buildActivity()

Robolectric’s buildActivity() method is a convenient way to create and configure an Activity instance for testing. It allows you to set up the Activity’s state, dependencies, and resources without requiring a physical device or emulator. This simplifies unit testing by isolating the Activity’s functionality from external factors.

Mockito Spy

Mockito spies are a specialized type of mock object that provide the ability to wrap real objects and intercept specific method calls. You can use spies to record interactions with the real object, stub out certain methods, or verify the expected behavior of the real object during testing.

Using buildActivity() with Mockito Spy

Combining buildActivity() with Mockito spies offers a highly effective testing strategy. Here’s a typical workflow:

1. Create a Spy of the Activity Class

“`java
Activity activity = Mockito.spy(MyActivity.class);
“`

In this code, we create a spy object of the MyActivity class using the Mockito.spy() method.

2. Build the Activity using Robolectric

“`java
ActivityController controller = Robolectric.buildActivity(MyActivity.class);
controller.create().get();
“`

We utilize Robolectric’s buildActivity() method to create a controller for MyActivity. The controller is used to initialize the activity using create() and get().

3. Interact with the Spy Object

You can now directly interact with the activity spy object. For example, you can call methods on it, record interactions using Mockito.verify(), or stub out methods using Mockito.when().

4. Perform Assertions

Finally, use assertion libraries like JUnit to validate the expected behavior of the Activity and its dependencies.

Example

Let’s illustrate this with an example of testing an Activity that interacts with a network service:

“`java
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.robolectric.Robolectric;
import org.robolectric.RobolectricTestRunner;
import static org.mockito.Mockito.*;

import android.app.Activity;
import android.content.Context;

@RunWith(RobolectricTestRunner.class)
public class MyActivityTest {

private MyActivity activity;
private NetworkService networkService;

@Before
public void setUp() {
activity = Mockito.spy(MyActivity.class);
networkService = Mockito.mock(NetworkService.class);
when(activity.getApplicationContext()).thenReturn(Robolectric.application.getApplicationContext());
when(activity.getSystemService(Context.NETWORK_SERVICE)).thenReturn(networkService);

ActivityController controller = Robolectric.buildActivity(MyActivity.class);
controller.create().get();
}

@Test
public void testLoadData() {
// Stub network response
when(networkService.fetchData()).thenReturn(“Data Loaded”);

activity.loadData();

// Verify network service call
verify(networkService).fetchData();
// Verify UI updates (using custom assertions)
// …
}
}
“`

In this example, we create a spy of MyActivity, mock the NetworkService, and stub its fetchData() method to return “Data Loaded”. We then call the loadData() method of the spy object and verify that the fetchData() method of the mocked network service was invoked.

Advantages of using buildActivity() with Mockito Spy

* **Isolation:** The buildActivity() method provides a controlled environment for testing, isolating the Activity from external dependencies.
* **Flexibility:** Mockito spies enable you to intercept specific method calls, stub out behavior, and record interactions, giving you fine-grained control over the testing process.
* **Testability:** Using spies simplifies the testing of complex activities with intricate interactions and dependencies.
* **Realistic Simulations:** Spies allow you to simulate realistic scenarios, such as network responses, database interactions, or user events.

Table: Robolectric buildActivity() vs. Mockito Spy

Conclusion

Combining Robolectric’s buildActivity() method with Mockito spies offers a powerful and flexible approach to testing Android Activities. By using spies, you can easily mock and stub out dependencies, isolate Activity behavior, and create robust test cases. This technique helps you write reliable and maintainable Android code by providing a comprehensive testing environment.