Test-driving Android GUI

It happened again that I received an e-mail from somebody asking whether there is a way to automate the testing of Android user interfaces. I did not know so I went after the issue and to my utter surprise, I discovered that an entire unit test framework has been developed into Android while I looked the other way. In this blog entry, I will describe my experiences with the Android instrumentation framework.

You can download the example program from here.

The idea behind Android instrumentation framework is that there are instrumentation components that resemble a lot the usual Activities. The purpose of these instrumentation components, however, is to test-drive other, normal Activities. Let's see the example program!

Install the package in the bin directory as usual:

adb install instrumentation-debug.apk

If the package has been installed before, you first have to uninstall it. This is new in the 1.0 version of the SDK, previously the new installation would simply overwrite the old one.

adb uninstall aexp.instrumentation

Two applications appear in the application folder. "Calculator" is a primitive calculator application used as test target. You can launch it independently and try it yourself. If you launch "Calculator instrumentation launcher", you will be confronted with a button to launch Calculator instrumentation. Once you push it, the calculator launches but its input keypresses will come from the instrumentation component. You will see the input fields filled up automatically, the addition button pushed and the result displayed. Then both the calculator instance and the launcher will disappear but if you check the logs (adb logcat), you will see that the test was successful.


The key instruction is in CalculatorInstrumentationLauncher.java where the instrumentation component is launched:

startInstrumentation(
new ComponentName(
CalculatorInstrumentationLauncher.this,
CalculatorInstrumentation.class ),
null,
null );

This launches CalculatorInstrumentation component which is a descendant of android.app.Instrumentation. The instrumentation component resembles a normal Activity, except that it is able to drive user input of other activities. This time we launch the Calculator, feed in keypresses (sendCharacterSync()) and invoke one of its method to obtain the result. Note the usage of runOnMainSync() method when we invoke Calculator's method to obtain the result.

It is definitely cool that Android has a user interface-oriented unit testing framework built into the platform. Maybe I am ignorant but I am not aware of any other platform that has this capability. In order to Test Driven Development (TDD), we need a proper unit testing framework and Android has even JUnit integrated. More about that later.