Lesson 4 - Java Testing - Unit Tests of Real Applications I

In the previous lesson, Java Testing - Hamcrest, JUnit TestRule and Best Practices, we introduced the Hamcrest library, the rules annotation, and finally we mentioned the best practices for testing in Java. To make sure we don't end with just our calculator's tests, we'll show unit test codes from real applications in the following few lessons. These will be tests of a message analyzer, persistence layer (data storage), and tests of a random token generator. They will help you get a better idea of how such things are tested in practice.

Note: The examples will get more and more complex. Don't worry if you don't understand something in their implementation. You should mainly understand how the tests work, which test verifies which features and how it does it.

Tag analyzer test

The following test verifies that the TagAnalyzer class works correctly. It analyzes a message and searches for hashtags, as you know them from Facebook ("I've overslept again. #mondays").

Let's take a look at the basic structure of the test class with initialization and describe it below.

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