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android – Assert proper number of items in list with espresso

Posted by: admin June 15, 2020 Leave a comment

Questions:

What is the best way to inspect and assert that a listview is the expected size with android espresso?

I wrote this matcher, but don’t quite know how to integrate it into the test.

public static Matcher<View> withListSize (final int size) {
    return new TypeSafeMatcher<View> () {
        @Override public boolean matchesSafely (final View view) {
            return ((ListView) view).getChildCount () == size;
        }

        @Override public void describeTo (final Description description) {
            description.appendText ("ListView should have " + size + " items");
        }
    };
}
How to&Answers:

Figured this out.

class Matchers {
  public static Matcher<View> withListSize (final int size) {
    return new TypeSafeMatcher<View> () {
      @Override public boolean matchesSafely (final View view) {
        return ((ListView) view).getCount () == size;
      }

      @Override public void describeTo (final Description description) {
        description.appendText ("ListView should have " + size + " items");
      }
    };
  }
}

If expecting one item in the list, put this in the actual test script.

onView (withId (android.R.id.list)).check (ViewAssertions.matches (Matchers.withListSize (1)));

Answer:

There are two different approaches of getting items count in a list with espresso:
First one is as @CoryRoy mentioned above – using TypeSafeMatcher, the other one is to use BoundedMatcher.

And because @CoryRoy already showed how to assert it, here I’d like to tell how to get(return) the number using different matchers.

public class CountHelper {

    private static int count;

    public static int getCountFromListUsingTypeSafeMatcher(@IdRes int listViewId) {
        count = 0;

        Matcher matcher = new TypeSafeMatcher<View>() {
            @Override
            protected boolean matchesSafely(View item) {
                count = ((ListView) item).getCount();
                return true;
            }

            @Override
            public void describeTo(Description description) {
            }
        };

        onView(withId(listViewId)).check(matches(matcher));

        int result = count;
        count = 0;
        return result;
    }

    public static int getCountFromListUsingBoundedMatcher(@IdRes int listViewId) {
        count = 0;

        Matcher<Object> matcher = new BoundedMatcher<Object, String>(String.class) {
            @Override
            protected boolean matchesSafely(String item) {
                count += 1;
                return true;
            }

            @Override
            public void describeTo(Description description) {
            }
        };

        try {
            // do a nonsense operation with no impact
            // because ViewMatchers would only start matching when action is performed on DataInteraction
            onData(matcher).inAdapterView(withId(listViewId)).perform(typeText(""));
        } catch (Exception e) {
        }

        int result = count;
        count = 0;
        return result;
    }

}

Also want to mention that you should use ListView#getCount() instead of ListView#getChildCount():

  • getCount() – number of data items owned by the Adapter, which may be larger than the number of visible views.
  • getChildCount() – number of children in the ViewGroup, which may be reused by the ViewGroup.