Recipe Wait for execution

IdlingResources is the concept from Espresso to sync with executions on non ui threads.

See also

• Espresso IdlingResource
• Espresso Guide

Use IdlingResource concept

Add idling resources as compile time dependency

compile 'com.android.support.test.espresso:espresso-idling-resource:2.2.2'

Implement a basic counting idling resource

public class MyIdlingResource implements IdlingResource {

    private static MyIdlingResource instance;

    private int count = 0;
    private ResourceCallback callback;

    public static MyIdlingResource instance() {
        if(instance == null) {
            instance = new MyIdlingResource();
        }
        return instance;
    }

    private MyIdlingResource() {
        // just hide constructor
    }

    public void increment() {
        count++;
    }

    public void decrement() {
        count--;
        if(count < 0) throw new IllegalStateException();
        if(count == 0 && callback != null) callback. onTransitionToIdle() 
    }

    @Override public String getName() {
        return MyIdlingResource.class.getSimpleName();
    }

    @Override public boolean isIdleNow() {
        return count == 0;
    }

    @Override public void registerIdleTransitionCallback(ResourceCallback resourceCallback) {
        this.callback = resourceCallback;
    }
}

In your test register your idling resource

Espresso.registerIdlingResources(MyIdlingResource.instance());

Use idling resource for non ui thread tasks

public void myAsyncMethod() {
    myIdlingResource.increment();
    ... tasks ...
    myIdlingResource.decrement();
}

Here a more stable usage example

public void myAsyncMethod() {
    try {
        myIdlingResource.increment();
        ... tasks ...
    } finally {
        myIdlingResource.decrement();
    }
}

CountingIdlingResource from espresso-contrib

Espresso self provides an implementation of the IdlingResource but it lead in much unused dependencies for your application.

See also

• http://developer.android.com/reference/android/support/test/espresso/contrib/CountingIdlingResource.html