Rubytest is a universal test harness for Ruby developers. You can think of Rubytest as a testing meta-framework. It defines a straight-forward specification that anyone can use to easily create their own testing DSLs. This can be used for testing end applications directly or it can be used as a backend to build other test frameworks. In addition, since Rubytest controls the backend, multiple frameworks can be used in a single test suite all of which can run through a uniform interface in a single pass.

Rubytest's clean specification makes it almost trivial to implement new test suites and frameworks. The universal access point for testing is the $TEST_SUITE global array. A test suite or framework need only add compliant test objects to this array. Rubytest will iterate through these objects. If a test object responds to #call, it is run as a test procedure. If it responds to #each it is iterated over as a testcase with each entry handled in the same manner. All test objects must respond to #to_s so their description can be used in test reports.

Ruby Test handles assertions via BRASS compliance. Any raised exception that responds to #assertion? in the affirmative is taken to be a failed assertion rather than simply an error. A test framework may raise a NotImplementedError to have a test recorded as todo, i.e. a pending exception to remind the developer of tests that still need to be written.