Randomized Runner

RandomizedRunner is a JUnit runner, so it is capable of running @Test-annotated test cases. It respects regular lifecycle hooks such as @Before, @After, @BeforeClass or @AfterClass, but it also adds the following:

Randomized, but repeatable execution and infrastructure for dealing with randomness:

• uses pseudo-randomness (so that a given run can be repeated if given the same starting seed) for many things called "random" below,
• randomly shuffles test methods to ensure they don't depend on each other,
• randomly shuffles hooks (within a given class) to ensure they don't depend on each other,
• base class RandomizedTest provides a number of methods for generating random numbers, strings and picking random objects from collections (again, this is fully repeatable given the initial seed if there are no race conditions),
• the runner provides infrastructure to augment stack traces with information about the initial seeds used for running the test, so that it can be repeated (or it can be determined that the test is not repeatable -- this indicates a problem with the test case itself).

Thread control:

• any threads created as part of a test case are assigned the same initial random seed (repeatability),
• tracks and attempts to terminate any Threads that are created and not terminated inside a test case (not cleaning up causes a test failure),
• tracks and attempts to terminate test cases that run for too long (default timeout: 60 seconds, adjustable using global property or annotations),

Improved validation and lifecycle support:

• RandomizedRunner uses relaxed contracts of hook methods' accessibility (hook methods can be private). This helps in avoiding problems with method shadowing (static hooks) or overrides that require tedious super.() chaining). Private hooks are always executed and don't affect subclasses in any way, period.
• @Listeners annotation on a test class allows it to hook into the execution progress and listen to events.
• @Validators annotation allows a test class to provide custom validation strategies (project-specific). For example a base class can request specific test case naming strategy (or reject JUnit3-like methods, for instance).
• RandomizedRunner does not "chain" or "suppress" exceptions happening during execution of a test case (including hooks). All exceptions are reported as soon as they happened and multiple failure reports can occur. Most environments we know of then display these failures sequentially allowing a clearer understanding of what actually happened first.

How to use it?

• The simple way: extend RandomizedTest.
• Annotate your class to use: @With(RandomizedRunner.class) and get RandomizedContext.current() manually.

Take a look at the examples and test cases of the runner itself.