Writing Your First Test
Let's say that you have an Activity that represents a welcome screen:
public class WelcomeActivity extends Activity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.welcome_activity);
final Button button = findViewById(R.id.login);
button.setOnClickListener((view) -> {
startActivity(new Intent(WelcomeActivity.this, LoginActivity.class))
});
}
}
class WelcomeActivity : Activity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.welcome_activity)
val button = findViewById<Button>(R.id.login)
button.setOnClickListener {
startActivity(Intent(this, LoginActivity::class.java))
}
}
}
<?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 the user clicks on the "Login" button, the app launches the LoginActivity.
To achieve this, we can check that the correct Intent is started when the click is performed. Since Robolectric is a unit testing framework, the LoginActivity will not actually be started.
@RunWith(RobolectricTestRunner.class)
public class WelcomeActivityTest {
@Test
public void clickingLogin_shouldStartLoginActivity() {
try (ActivityController<WelcomeActivity> controller = Robolectric.buildActivity(WelcomeActivity.class)) {
controller.setup(); // Moves the Activity to the RESUMED state
WelcomeActivity activity = controller.get();
activity.findViewById<Button>(R.id.login).performClick();
Intent expectedIntent = new Intent(activity, LoginActivity.class);
Intent actual = shadowOf(RuntimeEnvironment.application).getNextStartedActivity();
assertEquals(expectedIntent.getComponent(), actual.getComponent());
}
}
}
@RunWith(RobolectricTestRunner::class)
class WelcomeActivityTest {
@Test
fun clickingLogin_shouldStartLoginActivity() {
Robolectric.buildActivity(WelcomeActivity::class.java).use { controller ->
controller.setup() // Moves the Activity to the RESUMED state
val activity = controller.get()
activity.findViewById<Button>(R.id.login).performClick()
val expectedIntent = Intent(activity, LoginActivity::class.java)
val actual = shadowOf(RuntimeEnvironment.application).nextStartedActivity
assertEquals(expectedIntent.component, actual.component)
}
}
}
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 are useful for tests.
Many test APIs are extensions to individual Android classes, and can be accessed using the shadowOf() method:
Additional test APIs are accessible as static methods on special classes called shadows, which correspond to Android framework classes: