Writing Your First Test
Let's say you have an activity layout that represents a welcome screen:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/login"
android:text="Login"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
We want to write a test that asserts that when a user clicks on a button, the app launches the LoginActivity.
public class WelcomeActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.welcome_activity);
final View button = findViewById(R.id.login);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(WelcomeActivity.this, LoginActivity.class));
}
});
}
}
In order to test this, we can check that when a user clicks on the "Login" button, we start the correct intent. Because Robolectric is a unit testing framework, the LoginActivity will not actually be started, but we can check that the WelcomeActivity fired the correct intent:
@RunWith(RobolectricTestRunner.class)
public class WelcomeActivityTest {
@Test
public void clickingLogin_shouldStartLoginActivity() {
try (ActivityController<WelcomeActivity> controller = Robolectric.buildActivity(WelcomeActivity.class)) {
controller.setup(); // Moves Activity to RESUMED state
WelcomeActivity activity = controller.get();
activity.findViewById(R.id.login).performClick();
Intent expectedIntent = new Intent(activity, LoginActivity.class);
Intent actual = shadowOf(RuntimeEnvironment.application).getNextStartedActivity();
assertEquals(expectedIntent.getComponent(), actual.getComponent());
}
}
}
Test APIs
Robolectric extends the Android framework with a large set of test APIs, which offer extra configurability and access to the internal state and history of Android components that's useful for tests.
Many test APIs are extensions to individual Android classes, and can be accessed using the shadowOf() method:
// retrieves all the toasts that have been displayed...
List<Toast> toasts = shadowOf(application).getShownToasts();
Additional test APIs are accessible as static methods on special classes called shadows, which correspond to Android framework classes: