RecyclerViewSizeMatcher: Custom Espresso Matcher to check the size of a RecyclerView

RecyclerViewSizeMatcher.java

public static Matcher<View> recyclerViewSizeMatcher(final int matcherSize) {
    return new BoundedMatcher<View, RecyclerView>(RecyclerView.class) {
        @Override
        public void describeTo(Description description) {
            description.appendText("with list size: " + matcherSize);
        }

        @Override
        protected boolean matchesSafely(RecyclerView recyclerView) {
            return matcherSize == recyclerView.getAdapter().getItemCount();
        }
    };
}

//how to use it:
onView(withId(R.id.my_list_recycler)).check(matches(recyclerViewSizeMatcher(4)));