Hard Mock Cafe

In the first part , I gave you a brief introduction to the basic functionality of the new JUnit 5 framework: new asserts, testing exceptions and timing, parameterizing and structuring tests. In this part I will explain the extension mechanism, which serves as a replacement for the runners and rules. The New Extension Model JUnit 4 introduced the concept of runners, which allowed you to implement a strategy on how to run a test. You could specify the runner to use by attaching the @RunWith annotation to the test class, where the value of the annotation specified the runner class to use. You could do quite a lot of stuff with runners, but they had one central drawback: you could specify only one runner on a test :-| Since this was not flexible enough for most people, they invented the concept of rules. Rules allows you to intercept the test execution, so you can do all kind of stuff here like test preparation and cleanup, but also conditionally executing a test. Additionally y...

More than a decade ago I wrote an  introduction to JUnit 4 , which was – to be quite honest – just a catch-up with the more advanced TestNG. Now JUnit 5 is in the door and it is a complete rewrite, so it’s worth having a fresh look on it. In the first installment of this two part article I will describe what’s new in the basic usage: new asserts, testing exceptions and timing, parameterizing and structuring tests. JUnit 5 comes with a comprehensive user guide , most examples shown in this part are taken from there. So if you already read that, you may skip this and continue directly with the second part, which describes the new extension API that replaces the old runner and rules mechanisms. One Jar fits all? Prior to JUnit 5 all parts of the JUnit framework has been packed into one jar: the API to write tests - e.g. assertions - and the API and implementation to actually run tests; for some time, even hamcrest was baked into it. This was a problem ...