jtreg is the test harness used by the OpenJDK test framework. This framework is intended primarily for regression tests. It can also be used for unit tests, functional tests, and even simple product tests -- in other words, just about any type of test except a conformance test, which belong in a TCK. jtreg currently supports over 10,000 tests that have been written for the JDK.
Balchandra Vaidya, technical staff member at Oracle, gave a jtreg tutorial at a TestFest hosted by the London Java Community. The presentation was broken into four sections and all are now available on the Oracle Java YouTube channel. Part 1 is called Getting started with JTREG, it includes an introduction on using jtreg. The nuts and bolts of a jtreg test case, how to execute a jtreg test case, an example of a test case and a review of the log file produced. A demo of the example is also included and finally some links to reference materials.