Testing the coverage metric of JMockIt


After yesterdays article about Code Coverage terminology I thought more about the code coverage metric JMockIt uses. I created a simple class and a unit test to get more insights:

This is as simple as it gets. The example is taken from the Wikipedia page on Kontrollflussorientierte Testverfahren again. For 100% statement coverage you only need one test case, in which y > x. Then all statements are executed and you have 100% statement coverage.

And here is the resulting JMockit coverage report:

As you can see, JMockit tells us that every single statement is executed, exactly 1 time, with this test case. And that's exactly what I understand as statement coverage and it is in full compliance to the ISTQB terminology. Now, to make my point really clear, let me change the class as follows:

I added the empty ELSE statement that I omitted first. And I run JMockit again to get a new coverage report:

This is not 100% branch coverage, ISTQB certified or not. ;-) My point on this is, if you want to use a tool to verify your testing requirements, make sure that you know what the tool is measuring. And make sure you read the discussion thread in the JMockit users group.

*Update* I created a Cobertura coverage report for CoverMeSimple now:

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