How can I get activity's resources inside a test?

I am learning how to test from this section in the tutorial. In the tutorial they say to write the following code in the test's class:

@RunWith(AndroidJUnit4.class)
public class ActivityInputOutputTest {
   @Rule
   public ActivityTestRule mActivityRule = new ActivityTestRule<>(
                     MainActivity.class);
}

After I couldn't import ActivityTestRule properly, I researched and found out here that I should use ActivityScenarioRule instead of ActivityTestRule. So the code that I currently have is this:

@RunWith(AndroidJUnit4.class)
public class SpinnerSelectionTest {

    @Rule
    public ActivityScenarioRule mActivityRule = new ActivityScenarioRule<>(
            MainActivity.class);
}

Then, in the tutorial (section 3.2) they say to add this code:

public void iterateSpinnerItems() {
   String[] myArray =
         mActivityRule.getActivity().getResources()
         .getStringArray(R.array.labels_array);
}

Obviusely it doesn't work because my mActivityRule' type is different from the type in the tutorial.

How can I implement their code where I use ActivityScenarioRule as a type to mActivityRule. Is there equivalent code in my type that can help me?