minitest provides a complete suite of testing facilities supporting TDD, BDD, mocking, and benchmarking.
Hunting down random test failures can be very very difficult, sometimes impossible, but minitest-bisect makes it easy.
Graph is a type of hash that outputs in graphviz's dot format. It comes with a command-line interface that is easily pluggable.
A minitest plugin that adds a report of the top tests by number of objects allocated.