minitest provides a complete suite of testing facilities supporting TDD,
BDD, mocking, and benchmarking.

minitest/unit is a small and incredibly fast unit testing framework. It
provides a rich set of assertions to make your tests clean and readable.

minitest/spec is a functionally complete spec engine. It hooks onto
minitest/unit and seamlessly bridges test assertions over to spec
expectations.

minitest/benchmark is an awesome way to assert the performance of your
algorithms in a repeatable manner.

minitest/mock by Steven Baker, is a beautifully tiny mock (and stub)
object framework.

minitest/pride shows pride in testing and adds coloring to your test
output.

minitest/unit is meant to have a clean implementation for language
implementors that need a minimal set of methods to bootstrap a working
test suite. For example, there is no magic involved for test-case
discovery.