How to: Execute RSpec in parallel locally

So far we used Knapsack gem for dividing our tests in order to evenly run them on CI, but we can’t really use it for running them all in parallel locally. This is where ParallelTests gem will come in handy.ParallelTests splits tests into even groups (by the number of lines or runtime) and runs each group in a single process with its own database.So in short, each process spawned by ParallelTests should have its resources isolated from one another, so they don’t interfere with each other.