Assert proper number of items in list with espresso

Question

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");
        }
    };
}

Answer 1

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)));