Mocking classes in Android with JMock, JMockIt or EasyMock

* I stand corrected.  A commenter, Kiran Gunda, says it’s possible to mock f inal methods with JMockIt.  I may have set the mock up incorrectly.  If I try again, I’ll update this post.  Until then, an updated post describes how I used Android test classes to run my code.  Matt also pointed out that JMock can mock final methods using JDave’s unfinalizer.

* Updated July 11, 2009 to remove some incorrect information

So that you don’t have to read this whole post, I’ll sumarize what I discovered.  If you’re thinking about using a mocking library to mock Android classes, don’t.  Android uses interfaces sparsely.  That makes a clean API with lots of reusable code, but makes mocking difficult.  The real problem, though, is caused by Android’s generous use of final methods.  I don’t know of any mocking library that can mock final methods, so you just can’t do it.  Instead of writing mocks, look into the android.test and android.test.mock packages.

I developed GreenMileage so that I could learn about the Android OS.  Now that I have an understanding of it, I decided to go back and write test cases so that I could continue development using TDD.  I started by writing tests for utility classes.  That wasn’t a problem.  After finishing that, I moved to some simple UI cases.  The first was TextViewCallbackListener.  I just had to mock TextView.setText(String).

First, I spent hours just trying to get the JMock jars into the project.  For some reason, the compiler would not put JMock into the APK.  I didn’t get any error message or notification.  It just wasn’t there.

I decided to use Android’s test mocks to run my code.  Click here to see a simple example.

Posted in Android at May 30th, 2009. 5 Comments.