Test Observable subscriber behaviour

I'm writing a test to check the behaviour of my subscriber. I have a method like that:

public void myMethod(){
     myObservable.subscribe(result -> {
         count++;
     })

}

I want to test that myMethod increments count variable when result is emmited, but because count is incremented asynchronously, I need to wait until result is emmited to check count status. How can I do that?