The consultancy Evil Martians released a ruby gem called TestProf which can be used to profile and improve a test suite. It works with both MiniTest and RSpec, but has a much higher feature set and usability with the latter. The gem has many tools built within it, and requires thorough exploration. The documentation contains an explicit playbook for how to profile and improve your tests.
AnyFixture - setup a shared context once at the start of the suite run and re-use throughout the suite.