Lesson 3 - Java Testing - Hamcrest, JUnit TestRule and Best Practices
In the previous lesson, Java Testing - The first unit test in JUnit, we introduced the very basics of JUnit and wrote our first unit test. In today's lesson, we're going to complete unit tests by introducing the Hamcrest library, which is newly supported by JUnit, and fundamentally changes the way we write assertions. We'll also discuss rules (TestRules) and at the end we'll mention best practices for writing unit tests.
Since JUnit 4.4, there's the
assertThat() method available,
bringing a new way to do asserts using Matchers from the
Hamcrest library. By combining these matchers, we can create a complex
expression easily. You may not be surprised that matchers are classes (again)
with static methods, we can chain them and we're also able to write custom
matchers. Using this new method results in great readability.
Let's see what one simple assertion would look like in the original syntax:
assertEquals(2, calculator.add(1, 1));
and now in Hamcrest:
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In this tutorial, we'll rewrite the previous unit test to the more modern syntax of the Hamcrest library, introduce TestRule API and best practices.
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