Unit tests for ONOS are built using the JUnit framework, version 4.11. Unit tests are used to verify correctness of implementations and are run as part of every full build of ONOS. The nightly SonarQube build runs all of the unit tests and produces coverage data that can be seen here.

Unit tests should be as short, fast and reliable as they can be.  Every developer on the project will be running your tests, they should be easy to run and produce accurate results. Here are some key ways to write tests that are not brittle:

• Don't use sleep(), since it often leads to brittle tests.  If you find that you have to wait for an event or wait for some work to be done by another thread, prefer latches or thread notifications to sleeps.
• Try to keep individual tests small, and only test one thing per test.
• Use mocking when you need to include a complicated service to satisfy dependencies.
• Maven may choose to run multiple tests in the same Java virtual machine.  If you use static variables in classes, be sure to reset them to known starting values before each test runs.
• Do not use local resources like files and IP Addresses in tests.

We use the Hamcrest matchers, version 1.3.