JUnit tests are only valuable if they are executed regularly. This section explains the general purpose of continuous integration builds, which ascertains a high test execution frequency. Hence, CI constitutes a very good match to the test first approach.
In Chapter 1, Getting Started, we mentioned the importance of immediate feedback with respect to unit testing. If we bust some low-level functionality, we want to know about it as soon as possible. This puts us in a position to detect and correct a problem as it evolves and avoid expensive quality assurance cycles. Because of this, it's good practice to run all tests at least once after merging and before checking in changes into Version Control System (VCS). This reduces the risk of spoiling a teammate's day.
To give an impression, the following screenshot shows a test run of the complete test universe of the timeline sample:
AllTestSuite
AllTestSuite includes unit and integration...