MainActivityTest.java

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

    @Rule
    public ActivityTestRule<MainActivity> mActivityTestRule = new ActivityTestRule<>(MainActivity.class);

    @Test
    public void mainActivityTest() {
        ViewInteraction textView = onView(
                allOf(withId(R.id.textview), withText("Hello World"),
                        childAtPosition(
                                allOf(withId(R.id.text_switcher),
                                        childAtPosition(
                                                IsInstanceOf.<View>instanceOf(android.widget.RelativeLayout.class),
                                                1)),
                                0),
                        isDisplayed()));
        textView.check(matches(withText("Hello World")));

        ViewInteraction appCompatButton = onView(
                allOf(withId(R.id.button), withText("Click"), isDisplayed()));
        appCompatButton.perform(click());
        try {
            Thread.sleep(300);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        ViewInteraction textView2 = onView(
                allOf(withId(R.id.textview), withText("Bye World"),
                        childAtPosition(
                                allOf(withId(R.id.text_switcher),
                                        childAtPosition(
                                                IsInstanceOf.<View>instanceOf(android.widget.RelativeLayout.class),
                                                1)),
                                0),
                        isDisplayed()));
        textView2.check(matches(withText("Bye World")));

    }

    private static Matcher<View> childAtPosition(
            final Matcher<View> parentMatcher, final int position) {

        return new TypeSafeMatcher<View>() {
            @Override
            public void describeTo(Description description) {
                description.appendText("Child at position " + position + " in parent ");
                parentMatcher.describeTo(description);
            }

            @Override
            public boolean matchesSafely(View view) {
                ViewParent parent = view.getParent();
                return parent instanceof ViewGroup && parentMatcher.matches(parent)
                        && view.equals(((ViewGroup) parent).getChildAt(position));
            }
        };
    }
}