Question: how to do tdd in android?
Answer: Add a test: Anytime you start a new feature, fix or refactor, you write a test for it. ... 
Run it and watch it fail: Here, you run the tests. ... 
Write the code to make the test pass: This is when you write your feature, fix or refactor. ... 
Run the tests and see them pass: Now, you get to run the tests again!