ActivityInstrumentationTestCase2 vs ActivityTestRule

Question

I need to test a single activity in my Android app. The documentation of ActivityInstrumentationTestCase2 says:

This class provides functional testing of a single activity.

And the documentation of ActivityTestRule says:

This rule provides functional testing of a single activity.

Almost the same words. Besides the two samples I've coded, do the same. So should I prefer ActivityTestRule over ActivityInstrumentationTestCase2 or vice versa?

What I see is that extending ActivityInstrumentationTestCase2 looks like a JUnit3-styled test (its ancestor is junit.framework.TestCase, and test methods should start with the word test).

Using ActivityTestRule

package sample.com.sample_project_2;

import android.support.test.rule.ActivityTestRule;
import android.support.test.runner.AndroidJUnit4;
import android.test.suitebuilder.annotation.LargeTest;

import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.action.ViewActions.typeText;
import static android.support.test.espresso.matcher.ViewMatchers.withId;

@RunWith(AndroidJUnit4.class)
@LargeTest
public class ApplicationTest {

    @Rule
    public ActivityTestRule<SecAct> mActivityRule = new ActivityTestRule(SecAct.class);

    @Test
    public void foo() {
        onView(withId(R.id.editTextUserInput)).perform(typeText("SAMPLE"));

    }
}

Extending ActivityInstrumentationTestCase2

package sample.com.sample_project_2;

import android.test.ActivityInstrumentationTestCase2;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.action.ViewActions.typeText;
import static android.support.test.espresso.matcher.ViewMatchers.withId;


public class ApplicationTest2 extends ActivityInstrumentationTestCase2<SecAct> {

    public ApplicationTest2() {
        super(SecAct.class);
    }

    @Override
    protected void setUp() throws Exception {
        super.setUp();
        getActivity();
    }


    public void testFoo2() {
        onView(withId(R.id.editTextUserInput)).perform(typeText("SAMPLE 2"));

    }
}

Answer 1

For your example, there is no difference. You can use any of them.

As per OO principle we shall "Prefer composition over inheritance". Usage of ActivityTestRule<> is through composition while ActivityInstrumentationTestCase2<> is though inheritance.

At times, I prefer to have a common base class for my test classes to reuse common initializations. This helps me to group tests according to a theme. ActivityTestRule<> allows me to do such things.

For these reasons, I prefer ActivityTestRule<>. Otherwise, I haven't seen any difference.