How do I make Espresso wait until Data Binding has updated the View with the data-model?

Question

I am running Espresso tests on my Android application. The test is flaky. It can reliable assert that the data-model is updated. My problem is that the ViewMatchers can\'t m

Answer 1

Edit: This is an old answer. Please use Roshak's

The bug report mentioned using reflection to change ViewDataBinding.USE_CHOREOGRAPHER to false for the tests, so here is the solution I came up with:

public static void setFinalStatic(Field field, Object newValue) throws Exception {
    field.setAccessible(true);

    Field modifiersField;
    try {
        modifiersField = Field.class.getDeclaredField("accessFlags");
    } catch(NoSuchFieldException e) {
        //This is an emulator JVM  ¯\_(ツ)_/¯
        modifiersField = Field.class.getDeclaredField("modifiers");
    }
    modifiersField.setAccessible(true);
    modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

    field.set(null, newValue);
}

Then, just define an ActivityTestRule for the Activity under test, and override its beforeActivityLaunched(). It is necessary to do this before the activity is launched (as opposed to in a @Before annotation) because ViewDataBinding will initialize a Looper if it doesn't use CHOREOGRAPHER.

@Override
protected void beforeActivityLaunched() {
    super.beforeActivityLaunched();
    //Because we are using data-binding, we avoid using CHOREOGRAPHER
    try {
        ReflectionUtils.setFinalStatic(
           ViewDataBinding.class.getDeclaredField("USE_CHOREOGRAPHER"), false);
    } catch (Exception e) {
        Assert.fail(e.getMessage());
    }
}

This way, you can get rid of that Thread.sleep()