January 21, 2021
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Adding a JUnit Unit Test to Android, Page 2

  • By Lauren Darcey & Shane Conder
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Adding a Unit Test to Android

You can craft tests for all sorts of reasons. You have access to all the screen controls on the Activity's layout as well as any code in your app. Since we're using an activity test case, we're probably interested in something to do with the user interface, the Activity's layout, or its functionality. Let's find out if the TextView control fits on the screen.

public void testHelloTextVisibility() { 
   View container = getActivity().findViewById(R.id.container_layout); 
   int boundaryWidth = container.getWidth(); 
   int boundaryHeight = container.getHeight(); 

   int[] location = new int[2]; 

   int[] helloTextLocation = new int[2]; 

   Rect textRect = new Rect(); 

   boolean widerThanBoundary = (textRect.width() > boundaryWidth); 
   boolean tallerThanBoundary = (textRect.height() > boundaryHeight); 
   boolean extendsOffRight = location[0] + boundaryWidth 
     > helloTextLocation[0] + textRect.width(); 
   assertTrue("Text wider than boundary", widerThanBoundary); 
   assertTrue("Text taller than boundary", tallerThanBoundary); 
   assertTrue("Text goes off right side", extendsOffRight); 

   // ... and so on 

All test methods must start with "test" followed by a descriptive test name. In this case, we've created a test named "Hello Text Visibility." The assertFalse() calls are what determine if the test ultimately passes or fails. (The assertTrue() method can be used as well, for values that must be true to pass.)

Running Android Test Cases with JUnit

To run tests and tests cases you've created, click on the Debug drop down from within Eclipse, choose Debug As, then Android JUnit Test. You can also create an Android JUnit Test configuration to customize these settings, if you prefer.

Our little app passes the "Hello Text Visibility" test with flying colors… when our device is in landscape mode:

Eclipse showing Android JUnit test case pass

...But when in portrait mode, our Activity fails the test:

Eclipse showing Android JUnit Test case failure

Apparently our layout isn't designed to display correctly in portrait mode. (Hint: Perhaps this has something to do with setting the width to more pixels than the phone has rather than using a more appropriate unit like dp or just match_parent.)

You should run your tests on all target devices and configurations you expect to support. Our simple unit test example has more overhead per test than you'd normally find. If your test takes a long time to run, you may want to set up several to run in parallel.

Android App Quality Only As Good As the Unit Tests

Care must be taken when creating unit tests. If a test passes but isn't testing for the correct values and behaviors, that won't produce any sort of useful results. In fact, it can be dangerous as it might mask problems. The development of test cases is just as important as the development of the code itself. The primary way to test the test cases is by doing careful code reviews and make sure they're testing what you think they are.

It's also not particularly useful to your app to test Android (or Java) framework functionality. For example, performing a test where you set the text value on a field and then read it back to see if it's the same. If the test is being performed on a regular TextView, the test won't be particularly meaningful (unless you're implementing the SDK on a new device). However, if you've creating your own implementation of TextView, by all means--test it. In other words, testing tautologies isn't a very good use of time and resources.

That's not to say that any code base is bug free, but testing things that are equivalent to testing if one equals one isn't worth the effort to write the test to begin with. If that fails, you've got bigger problems than your app. There's also a subtle difference between testing the SDK and testing that we're using the SDK correctly (in the above example, we weren't).

Therefore, if you're new to automated unit testing in general, we recommend you do some research into the subject. A good place to start is JUnit.org.


In this tutorial, you've learned how to quickly add a new test project to your Android project in Eclipse in order to perform automated tests on your application using JUnit. Unit testing allows for logical testing, functional testing, and even user interface testing and validation. No longer are you forced to manually test your mobile applications exclusively. Including automated unit testing suites as part of your test plan has several big benefits: it can save time, money and resources as well as provide a set of reliable, reproducible tests that can be run across many different device configurations.

About the Authors

Shane Conder Shane Conder and Lauren Darcey--Contributing Editors, Mobile Development--have coauthored two books on Android development: an in-depth programming book entitled Android Wireless Application Development (ISBN-13: 978-0-321-62709-4) and Sams Teach Yourself Android Application Development in 24 Hours (ISBN-13: 978-0-321-67335-0). When not writing, they spend their time developing mobile software at their company and providing consulting services.

Email        |        Blog        |        Twitter

Lauren Darcey

Originally published on https://www.developer.com.

Page 2 of 2

This article was originally published on August 17, 2011

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