How to test android application using android studio?

i am an QA i am performing Manual Testing for testing the Android Applications.

Now, i am planning to test android applications by using automation tools. i tried Robotium. it seemed to an paid version. so i dropped Robotium.

i am preferring Android studio. i am not having sufficient knowledge over android studio.

While gathering data about this, i found Android Studio has Monkey and Monkey Runner. for Unit Testing.

Is there any other tool can be useful for Android Testing? and say how to test applications with that tools.