Android provides a testing framework for Service objects that can run them in isolation and provides mock objects. The test case class for Service objects is
ServiceTestCase. Since the Service class assumes that it is separate from its clients, you can test a Service object without using instrumentation.
This document describes techniques for testing Service objects. If you aren't familiar with the Service class, please read the Services document. If you aren't familiar with Android testing, please read Testing Fundamentals, the introduction to the Android testing and instrumentation framework.
When you design a Service, you should consider how your tests can examine the various states of the Service lifecycle. If the lifecycle methods that start up your Service, such as
onStartCommand() do not normally set a global variable to indicate that they were successful, you may want to provide such a variable for testing purposes.
Most other testing is facilitated by the methods in the
ServiceTestCase test case class. For example, the
getService() method returns a handle to the Service under test, which you can test to confirm that the Service is running even at the end of your tests.
ServiceTestCase extends the JUnit
TestCase class with with methods for testing application permissions and for controlling the application and Service under test. It also provides mock application and Context objects that isolate your test from the rest of the system.
ServiceTestCase defers initialization of the test environment until you call
ServiceTestCase.bindService(). This allows you to set up your test environment, particularly your mock objects, before the Service is started.
Notice that the parameters to
ServiceTestCase.bindService()are different from those for
Service.bindService(). For the
ServiceTestCase version, you only provide an Intent. Instead of returning a boolean,
ServiceTestCase.bindService() returns an object that subclasses
setUp() method for
ServiceTestCase is called before each test. It sets up the test fixture by making a copy of the current system Context before any test methods touch it. You can retrieve this Context by calling
getSystemContext(). If you override this method, you must call
super.setUp() as the first statement in the override.
setContext(Context) setContext()} allow you to set a mock Context or mock Application (or both) for the Service, before you start it. These mock objects are described in Mock object classes.
ServiceTestCase assumes that you will use a mock Context or mock Application (or both) for the test environment. These objects isolate the test environment from the rest of the system. If you don't provide your own instances of these objects before you start the Service, then
ServiceTestCase will create its own internal instances and inject them into the Service. You can override this behavior by creating and injecting your own instances before starting the Service
To inject a mock Application object into the Service under test, first create a subclass of
MockApplication is a subclass of
Application in which all the methods throw an Exception, so to use it effectively you subclass it and override the methods you need. You then inject it into the Service with the
setApplication() method. This mock object allows you to control the application values that the Service sees, and isolates it from the real system. In addition, any hidden dependencies your Service has on its application reveal themselves as exceptions when you run the test.
The topic What To Test lists general considerations for testing Android components. Here are some specific guidelines for testing a Service:
onCreate()is called in response to
Context.bindService(). Similarly, you should ensure that
onDestroy()is called in response to
Context.startService(). Only the first call triggers
Service.onCreate(), but all calls trigger a call to
In addition, remember that
startService() calls don't nest, so a single call to
Service.stopSelf() (but not
stopSelf(int)) will stop the Service. You should test that your Service stops at the correct point.