@Before
    public void setActivity() {
        mActivity = mActivityRule.getActivity();
    }
A JUnit {@link Rule @Rule} to launch your activity under test. This is a replacement
for {@link android.test.ActivityInstrumentationTestCase2}.
<p>
Rules are interceptors which are executed for each test method and will run before
any of your setup code in the {@link Before @Before} method.
<p>
{@link ActivityTestRule} will create and launch of the activity for you and also expose
the activity under test. To get a reference to the activity you can use
the {@link ActivityTestRule#getActivity()} method.
ui/espresso/MultiWindowSample/app/src/androidTest/java/com/example/android/testing/espresso/MultiWindowSample/MultiWindowTest.java