How to count RecyclerView items with Espresso

Here an example ViewAssertion to check RecyclerView item count

public class RecyclerViewItemCountAssertion implements ViewAssertion {
  private final int expectedCount;

  public RecyclerViewItemCountAssertion(int expectedCount) {
    this.expectedCount = expectedCount;
  }

  @Override
  public void check(View view, NoMatchingViewException noViewFoundException) {
    if (noViewFoundException != null) {
        throw noViewFoundException;
    }

    RecyclerView recyclerView = (RecyclerView) view;
    RecyclerView.Adapter adapter = recyclerView.getAdapter();
    assertThat(adapter.getItemCount(), is(expectedCount));
  }
}

and then use this assertion

onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(5));

I have started to write an library which should make testing more simple with espresso and uiautomator. This includes tooling for RecyclerView action and assertions. https://github.com/nenick/espresso-macchiato See for example EspRecyclerView with the method assertItemCountIs(int)

To complete nenick answer and provide and little bit more flexible solution to also test if item cout is greaterThan, lessThan ...

public class RecyclerViewItemCountAssertion implements ViewAssertion {

    private final Matcher<Integer> matcher;

    public RecyclerViewItemCountAssertion(int expectedCount) {
        this.matcher = is(expectedCount);
    }

    public RecyclerViewItemCountAssertion(Matcher<Integer> matcher) {
        this.matcher = matcher;
    }

    @Override
    public void check(View view, NoMatchingViewException noViewFoundException) {
        if (noViewFoundException != null) {
            throw noViewFoundException;
        }

        RecyclerView recyclerView = (RecyclerView) view;
        RecyclerView.Adapter adapter = recyclerView.getAdapter();
        assertThat(adapter.getItemCount(), matcher);
    }

}

Usage:

onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(5));
onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(greaterThan(5));
onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(lessThan(5));
// ...

Adding a bit of syntax sugar to the @Stephane's answer.

public class RecyclerViewItemCountAssertion implements ViewAssertion {
    private final Matcher<Integer> matcher;

    public static RecyclerViewItemCountAssertion withItemCount(int expectedCount) {
        return withItemCount(is(expectedCount));
    }

    public static RecyclerViewItemCountAssertion withItemCount(Matcher<Integer> matcher) {
        return new RecyclerViewItemCountAssertion(matcher);
    }

    private RecyclerViewItemCountAssertion(Matcher<Integer> matcher) {
        this.matcher = matcher;
    }

    @Override
    public void check(View view, NoMatchingViewException noViewFoundException) {
        if (noViewFoundException != null) {
            throw noViewFoundException;
        }

        RecyclerView recyclerView = (RecyclerView) view;
        RecyclerView.Adapter adapter = recyclerView.getAdapter();
        assertThat(adapter.getItemCount(), matcher);
    }
}

Usage:

    import static your.package.RecyclerViewItemCountAssertion.withItemCount;

    onView(withId(R.id.recyclerView)).check(withItemCount(5));
    onView(withId(R.id.recyclerView)).check(withItemCount(greaterThan(5)));
    onView(withId(R.id.recyclerView)).check(withItemCount(lessThan(5)));
    // ...