In this post we will try our hands at mocking/stubbing another exotic species called void static methods
Yes, I know void static methods should be avoided at all costs!
But sometimes you just cant help it!
So lets look at the code under test
In our example we want to test the upgradeAllCustomers method of the CustomerController.
This method upgrades all customers by invoking a void static method upgradeAll on Customer class. Currently implementation of upgradeAll method of Customer class throws and exception.
What do we want to test:
- upgradeAll void static method of Customer class was invoked
- true is returned after the upgrade
The syntax that we had seen in the earlier post will now work anymore
If we notice persist is an instance method on the Customer class (and the above syntax works for instance methods only).
But in this case we want to stub the void static method. How do we do it?
We have to do the following things
- Use the annotation @RunWith(PowerMockRunner.class) to bootstrap PowerMock itself
- Use the annotation @PrepareForTest(Customer.class) to be able to stub static methods of Customer class.
- Stub the void static method using the following lines of code
Notice that the syntax is a bit like record-playback-verify style.
We have to first tell PowerMock to do nothing when a static method is invoked on Customer class.
PowerMock should do nothing on which void static method is specified in the next line by invoking the void static upgradeAll method on the Customer class.
Its effectively recording the fact that, when static void upgradeAll method is invoked on Customer class nothing is to be done!
Before moving, lets see how can we verify that a void static method was actually invoked?
We can easily see that the syntax to verify that a static method was invoked also follows the record-playback-verify pattern.
First we have to inform PowerMock that we are going to verify a static method invocation, and in the next line we actually verify the call to the upgradeAll method.
Enough explanation lets look at the complete test code:
Yes thats how we do it!
For the first time I have to say, and believe me I hate to do so but, I don't like this syntax that much!
But that's just me and hats of to the excellent job that PowerMock and Mockito guys have done so far!