When you’re writing Espresso tests for your Android applications, you will often need to reference the resource id of a particular view in order to make your assertions. Instead of digging through code you can take advantage of the UIAutomatorViewer tool. It’s very simple to use and helps you to visualize the hierarchy of the views in your application. 

Here it is in action:

Espresso Test

@Test
public void clickOnDetailItemShouldDisplayPlayer() {
    onView(withId(R.id.container_list)).check(matches(isDisplayed()));
    onView(withId(R.id.browse_headers))
        .perform(pressKey(KeyEvent.KEYCODE_DPAD_RIGHT));

    onView(allOf(isDescendantOfA(
                     withRecyclerView(R.id.row_content).atPosition(0)),
           withId(R.id.info_field)))
              .perform(pressKey(KeyEvent.KEYCODE_DPAD_CENTER));

    onView(withId(R.id.wapo_player_view))
        .check(matches(isDisplayed()));
}