Create an observable of long click events on RecyclerView items (refer to RxBinding tests for the whole picture).

RecyclerViewItemLongClickOnSubscribe.java

import android.support.v7.widget.RecyclerView;
import android.view.View;

import rx.Observable;
import rx.Subscriber;
import rx.android.MainThreadSubscription;

import static rx.android.MainThreadSubscription.verifyMainThread;

final class RecyclerViewItemLongClickOnSubscribe implements Observable.OnSubscribe<Integer> {
  final RecyclerView recyclerView;

  public RecyclerViewItemLongClickOnSubscribe(RecyclerView recyclerView) {
    this.recyclerView = recyclerView;
  }

  @Override public void call(final Subscriber<? super Integer> subscriber) {
    verifyMainThread();

    final View.OnLongClickListener onLongClickListener = new View.OnLongClickListener() {
      @Override public boolean onLongClick(View view) {
        if (!subscriber.isUnsubscribed()) {
          RecyclerView.ViewHolder holder = recyclerView.getChildViewHolder(view);
          subscriber.onNext(holder.getAdapterPosition());
          return true;
        }
        return false;
      }
    };

    final RecyclerView.OnChildAttachStateChangeListener onAttachListener = new RecyclerView.OnChildAttachStateChangeListener() {
      @Override public void onChildViewAttachedToWindow(View view) {
        view.setOnLongClickListener(onLongClickListener);
      }

      @Override public void onChildViewDetachedFromWindow(View view) {
        view.setOnLongClickListener(null);
      }
    };

    subscriber.add(new MainThreadSubscription() {
      @Override protected void onUnsubscribe() {
        recyclerView.removeOnChildAttachStateChangeListener(onAttachListener);
      }
    });

    recyclerView.addOnChildAttachStateChangeListener(onAttachListener);
  }
}

RxRecyclerViewTest.java

@RunWith(AndroidJUnit4.class)
public final class RxRecyclerViewTest {
  @Rule public final ActivityTestRule<RxRecyclerViewTestActivity> activityRule =
      new ActivityTestRule<>(RxRecyclerViewTestActivity.class);

  private final Instrumentation instrumentation = InstrumentationRegistry.getInstrumentation();

  RecyclerView view;
  private ViewInteraction interaction;
  private ViewDirtyIdlingResource viewDirtyIdler;
  private View child;

  @Before public void setUp() {
    RxRecyclerViewTestActivity activity = activityRule.getActivity();
    view = activity.recyclerView;
    child = new View(activityRule.getActivity());
    interaction = Espresso.onView(ViewMatchers.withId(android.R.id.primary));
    viewDirtyIdler = new ViewDirtyIdlingResource(activity);
    Espresso.registerIdlingResources(viewDirtyIdler);
  }

  @After public void tearDown() {
    Espresso.unregisterIdlingResources(viewDirtyIdler);
  }

  @Test public void itemsClicked() {
    RecordingObserver<Integer> o = new RecordingObserver<>();
    Subscription subscription = RxRecyclerView.itemClick(view)
        .subscribeOn(AndroidSchedulers.mainThread())
        .subscribe(o);
    o.assertNoMoreEvents();

    final Adapter adapter = new Adapter();

    instrumentation.runOnMainSync(new Runnable() {
      @Override public void run() {
        view.setAdapter(adapter);
      }
    });
    for (int i = 0, childCount = view.getChildCount(); i < childCount; i++) {
      final View childAt = view.getChildAt(i);
      instrumentation.runOnMainSync(new Runnable() {
        @Override public void run() {
          childAt.performClick();
        }
      });
      assertThat(o.takeNext()).isEqualTo(i);
    }

    subscription.unsubscribe();

    instrumentation.runOnMainSync(new Runnable() {
      @Override public void run() {
        view.getChildAt(0).performClick();
      }
    });
    o.assertNoMoreEvents();
  }

  @Test public void itemsLongClicked() {
    RecordingObserver<Integer> o = new RecordingObserver<>();
    Subscription subscription = RxRecyclerView.itemLongClick(view)
        .subscribeOn(AndroidSchedulers.mainThread())
        .subscribe(o);
    o.assertNoMoreEvents();

    final Adapter adapter = new Adapter();

    instrumentation.runOnMainSync(new Runnable() {
      @Override public void run() {
        view.setAdapter(adapter);
      }
    });
    for (int i = 0, childCount = view.getChildCount(); i < childCount; i++) {
      final View childAt = view.getChildAt(i);
      instrumentation.runOnMainSync(new Runnable() {
        @Override public void run() {
          childAt.performLongClick();
        }
      });
      assertThat(o.takeNext()).isEqualTo(i);
    }

    subscription.unsubscribe();

    instrumentation.runOnMainSync(new Runnable() {
      @Override public void run() {
        view.getChildAt(0).performLongClick();
      }
    });
    o.assertNoMoreEvents();
  }

  private static class Adapter extends RecyclerView.Adapter<ViewHolder> {
    public Adapter() {
      setHasStableIds(true);
    }

    @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int position) {
      TextView v = (TextView) LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false);
      return new ViewHolder(v);
    }

    @Override public void onBindViewHolder(ViewHolder holder, int position) {
      holder.textView.setText(String.valueOf(position));
    }

    @Override public int getItemCount() {
      return 100;
    }

    @Override public long getItemId(int position) {
      return position;
    }
  }

  private static class ViewHolder extends RecyclerView.ViewHolder {

    TextView textView;

    public ViewHolder(TextView itemView) {
      super(itemView);
      this.textView = itemView;
    }
  }
}