Hello, espresso! Part 2 Working with lists

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In the previous post, we read an introduction to espresso, and understood how to write a basic test flow in espresso. We also saw the structure of an espresso test

In this post, we’ll dive into how to automate tests and work with list like components using espresso. Examples of such components are AdapterView,RecyclerView etc

Let’s go! 🏃🏃‍♀️

Working with lists in general

Using espresso, we can scroll to or perform an action on a given item in a list

This is needed since the view you are interested in may not be present on the screen since Android lists created with RecyclerView or AdapterView have only a small no of child elements created and they are recycled as you scroll. For these use cases scrollTo method won’t work as that needs an existing view

Let’s see an example and walk through how we could use espresso to scroll and act on elements for these types of components

Working with AdapterView

We’ll use DataAdapterSample for this post. You can find the app and test code atthispath in my forked Github repo

Understanding the app under test

Once you load the project in android studio and let gradle build it, you can run the app and see it load up on the emulator

Let’s understand the flow we want to automate a bit better

• we have a ListView component where each row has a TextView and aToggleButton
• You can scroll in this list
• Once you tap on a row, there is a LinearLayout at the top that’s set with the row no

Assume that we want to automate this flow

Using Layout Inspector to figure out the app structure

You don’t need to dive into the source code to figure out how everything would render on the UI when the app is built

Android studio provides a convenient tool called Layout Inspector , that allows us to inspect the Component Tree. (Kind of similar toAppium Inspector) You can open it by going to Tools > Layout Inspector , You’ll also need to select the process you want to inspect (In this case you can select DataAdapterSample)

Open layout inspector

Understanding the UI

The layout inspector has 3 main sections:

1. Component Tree: Here we can see the tree like structure that makes up our current screen, we can observe the ListView with TextView and Buttonand the static LinearLayout on top
2. Live App: This section is refreshed as you interact with your app in the emulator, you can select any particular row and it would highlight the same in Component Tree and also show the attributes
3. Attributes: Here we can see all the attributes or properties of the given element and use these while automating our tests in espresso

Writing our test for AdapterView

Let’s write our tests to perform the actions mentioned above

We’ll use a series of learning tests to explore how to test different aspects of this app and test and also learn espresso’s API a bit better, in a real test you may just write one test to perform the workflow you intend to test.

You can see the complete test fileherewith some helpful comments explaining what each test is supposed to do

Test control to be scrolled to is not visible

To start we want to create the usual structure i.e. Write our classDataAdapterPractice with @RunWith annotation and use ActivityScenarioRuleto start our LongListActivity activity

@RunWith(AndroidJUnit4.class)
@LargeTest

public class DataAdapterPractice {
    @Rule
    public ActivityScenarioRule<LongListActivity> rule = new ActivityScenarioRule<>(LongListActivity.class);
    ...

Before we try scrolling, it may be helpful to verify that the item that we want to scroll to (say a TextView with text: item: 99) does not exist, we can do that with below line:

onView(withText("item: 99")).check(doesNotExist());

Here is the complete test:

@RunWith(AndroidJUnit4.class)
@LargeTest

public class DataAdapterPractice {
    @Rule
    public ActivityScenarioRule<LongListActivity> rule = new ActivityScenarioRule<>(LongListActivity.class);

    @Test
    public void whenAppOpens_ThenLastItemIsNotDisplayed() {
        onView(withText("item: 99")).check(doesNotExist());
    }
}

Test we are able to scroll to last item

Next, we want to be able to scroll to the last item with text item: 99, we can figure out this text by actually scrolling in the app and then seeing the value of text attribute in the layout inspector

If we see the code forLongListActivitywe can see that the ListView gets its data from an adapter LongListAdapterthat has a hash map keys like ROW_TEXT and ROW_ENABLED

We can use this understanding to write our matcher to find this row

• To scroll to such an element we use onData instead of onView (since the element is not displayed on the view)
• In our test, We want to find the element whose ROW_TEXT is item:99 and we can do so using hasEntry Hamcrest matcher that is able to match elements in a hash map

onData(hasEntry(equalTo(LongListActivity.ROW_TEXT), is("item: 99")))

• Espresso would take care of automatically scrolling to this element for us
• We can then close the flow by checking that such a row is visible by using below ViewAssertion

.check(matches(isCompletelyDisplayed());

Below is how the complete test looks like:

@RunWith(AndroidJUnit4.class)
@LargeTest

public class DataAdapterPractice {
    @Rule
    public ActivityScenarioRule<LongListActivity> rule = new ActivityScenarioRule<>(LongListActivity.class);

    @Test
    public void whenScrollToLastItem_ThenLastItemIsDisplayed() {
        // We use onData since we want to scroll to an item in the list view
        // we use hasEntry matcher that takes two args, first the item check
        // and second the value
        onData(hasEntry(equalTo(LongListActivity.ROW_TEXT), is("item: 99")))
                // Then we check that this entry is displayed
                .check(matches(isCompletelyDisplayed()));
    }
}

Click on a row and verify the LinearLayout has expected test

If the user taps on a particular element in the ListView then the app updates the row no in a separate TextView with id: selection_row_value

We can repeat similar steps to scroll to the element with text value 30, tap on it and then check if the TextView at the top is updated with the correct value

To click on a child element inside a ListView we can use onChildView() method like below:

.onChildView(withId(R.id.rowContentTextView)).perform(click());

Below is how the complete test looks like:

@RunWith(AndroidJUnit4.class)
@LargeTest

public class DataAdapterPractice {
    @Rule
    public ActivityScenarioRule<LongListActivity> rule = new ActivityScenarioRule<>(LongListActivity.class);

    @Test
    public void whenClickOnRow_ThenTheTextIsUpdated() {
        String itemToClickOn = "item: 30";
        onData(hasEntry(equalTo(LongListActivity.ROW_TEXT), is(itemToClickOn)))
                // To click on an element in the list use `onChildView`
                .onChildView(withId(R.id.rowContentTextView)).perform(click());

        // Now that we are on desired item, we can verify using onView method
        String expectedValueAfterClick = "30";
        onView(withId(R.id.selection_row_value)).check(matches(withText(expectedValueAfterClick)));
    }
}

Working with RecyclerView

RecyclerView is a different type of list which ensures when the user scrolls off a screen, it recycles elements in an efficient manner. We do not useonData in this case. To understand how RecyclerView works you could readthis post on Android developers

To work with RecyclerView, we can use espresso-contrib package in our app’s gradle dependencies

androidTestImplementation 'androidx.test.espresso:espresso-contrib:' + rootProject.espressoVersion;

The dependency supports below actions:

Scrolling in a RecyclerView

• scrollTo() - Scroll to matched view
• scrollToHolder() - Scroll to matched view holder
• scrollToPosition() - Scroll to specific position

Performing action on element

• actionOnItem() - Perform view action on matched view
• actionOnHolderItem() - Perform view action on a matched View holder
• actionOnItemAtPosition() - Perform a view action on a view at a specific position

App under test

For these tests, we’ll useRecyclerViewSampletest app

In this test app, we have a RecyclerView where each row is a TextView having text like This is element #42, as the user scrolls the same elements are recycled and reused by Android framework

Learning tests

Let’s write some tests for this app

Test that a given element is not present in the list and espresso throws an exception

We’ll start with a negative test, what if we try to scroll to an element that does not exist, we should expect espresso framework to throw an exception in this case, this test also is a good way to demo the scrollTo method inRecyclerViewActions

• We use onView to find our RecyclerView (getting its id via layout inspector)

onView(withId(R.id.recyclerView))

• We then use scrollTo method in RecyclerViewActions and use hasDescendantViewMatcher to check that a hypothetical element with text not on the listis present. Naturally this throws an exception and we handle that by adding@Test(expected = PerformException.class) in the JUnit test assertion

.perform(RecyclerViewActions.scrollTo(hasDescendant(withText("not on the list"))));

Below is th how the complete test looks like:

@RunWith(AndroidJUnit4.class)
public class RecyclerViewSamplePracticeTest {

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

  /**
   * This is a negative test that tries to scroll to a descendant that does not exist in the app We
   * use Junit @Test annotation to verify that this test throws a PerformException
   */
  @Test(expected = PerformException.class)
  public void whenAppOpens_ThenItemWithTextIsNotVisible() {
    onView(withId(R.id.recyclerView))
        // Here scrollTo will fail if there are no items that match expected descriptions
        .perform(RecyclerViewActions.scrollTo(hasDescendant(withText("not on the list"))));
  }
}

Test we can scroll to a fixed position and click on it and check its displayed

Let’s say we want to scroll into our list to the 40th item and click on it, we use actionOnItemAtPosition method to specify the position and also add theclick() method to click that

onView(withId(R.id.recyclerView))
        .perform(RecyclerViewActions.actionOnItemAtPosition(itemBelowFold, click()));

We can then check if the item with expected text is displayed using below:

String expectedText = String.format("This is element #%d", itemBelowFold);
onView(withText(expectedText)).check(matches(isDisplayed()));

Below is how the complete test looks like:

@RunWith(AndroidJUnit4.class)
public class RecyclerViewSamplePracticeTest {

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

  /**
   * Test to scroll in a recycler view to an item at a fixed position And verify that the element
   * with expected text is displayed
   */
  @Test
  public void whenScrollToItemAtAPosition_ThenItemIsDisplayed() {
    int itemBelowFold = 40;
    onView(withId(R.id.recyclerView))
        .perform(RecyclerViewActions.actionOnItemAtPosition(itemBelowFold, click()));

    String expectedText = String.format("This is element #%d", itemBelowFold);
    onView(withText(expectedText)).check(matches(isDisplayed()));
  }
}

Test we can scroll to the middle using a custom matcher

Our app has a special row in the middle with a text: This is the middle!, let’s say we want to scroll to this elements holder and then verify its displayed

We can use scrollToHolder and pass it a custom matcher to verify if it has reached the middle

onView(withId(R.id.recyclerView)).perform(RecyclerViewActions.scrollToHolder(isInTheMiddle()));

Let’s see how isInTheMiddle() method is implemented

We create a new TypeSafeMatcher of type CustomAdapter.ViewHolder which overridden implementation of matchesSafely that returns getIsInTheMiddle()methods output. Note: The support for this method is added in apps source code

private static TypeSafeMatcher<CustomAdapter.ViewHolder> isInTheMiddle() {
    return new TypeSafeMatcher<CustomAdapter.ViewHolder>() {
      @Override
      public void describeTo(Description description) {
        description.appendText("item in the middle");
      }

      @Override
      protected boolean matchesSafely(CustomAdapter.ViewHolder viewHolder) {
        return viewHolder.getIsInTheMiddle();
      }
    };
  }

To see the app impl supporting this, seeCustomAdapterclass that has a method onBindViewHolder which sets this flag inviewHolder.setIsInTheMiddle(true); if the position == mDataSet.size() / 2

Finally, we can check if the view is displayed using:

String expectedText = String.format("This is element #%d", itemBelowFold);
onView(withText(expectedText)).check(matches(isDisplayed()));

Please see the complete test below:

@RunWith(AndroidJUnit4.class)
public class RecyclerViewSamplePracticeTest {

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

  /**
   * This test scrolls in recycler view till it finds an element with text: "This is the middle!" It
   * uses a field already set in the View holder implementation to determine it has reached the
   * point And a custom hamcrest matcher
   */
  @Test
  public void whenScrollToItemInTheMiddle_ThenCheckItemWithSpecialTextIsDisplayed() {
    onView(withId(R.id.recyclerView)).perform(RecyclerViewActions.scrollToHolder(isInTheMiddle()));

    onView(withText("This is the middle!")).check(matches(isDisplayed()));
  }

  private static TypeSafeMatcher<CustomAdapter.ViewHolder> isInTheMiddle() {
    return new TypeSafeMatcher<CustomAdapter.ViewHolder>() {
      @Override
      public void describeTo(Description description) {
        description.appendText("item in the middle");
      }

      @Override
      protected boolean matchesSafely(CustomAdapter.ViewHolder viewHolder) {
        return viewHolder.getIsInTheMiddle();
      }
    };
  }
}

Further reads

You can read Espresso lists on Android developers

Conclusion

Hopefully this post gives you an idea on how to work with list like components in espresso. Stay tuned for next post where we’ll dive into how to automate and work with intents with espresso

As always, Do share this with your friends or colleagues and if you have thoughts or feedback, I’d be more than happy to chat over at twitter or comments. Until next time. Happy Testing and coding.