Back in 1997, when JDK 1.1 was completed and JDK 1.2 had just started, there was an obvious problem—JDK had to be tested somehow and there had to be a tool for it. This is the moment when jtreg appeared as the regression test harness. At that time, there were not many testing frameworks for Java. In fact, there was not even much software written in Java. So choices were very limited and the only reasonable option was the framework that was being used at that time for the Java Compatibility Kit (JCK). Its name was JavaTest. But, as JCK tests were very different from what a JDK regression test is supposed to do, the framework required some adaptation and that is when jtreg appeared. At the moment, even though many years have passed since 1997, jtreg still remains the primary tool for running unit and regression tests in OpenJDK. Since its introduction in OpenJDK, more than 10,000 tests have been created that run using the jtreg framework.

As a testing tool, jtreg might look a...