Where did you see that? To be honest, if something is saying 0.0s, then it’s probably a measurement error 
Some key things we use to improve RSpec performance are:
-
GitHub - grosser/parallel_tests: Ruby: 2 CPUs = 2x Testing Speed for RSpec, Test::Unit and Cucumber
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test-prof/docs/recipes/let_it_be.md at master · test-prof/test-prof · GitHub (we wrap this in a
fab!helper in our codebase)