Testing Ruby Code Like a Pro: The Power of RSpec Mocks and Doubles
rubystacknews.com
rubystacknews.com
But don't get me wrong, I won't refuse using rspec if it's already set up for a project, just wish it wasn't the go to default. I do believe the ruby + rails code people write would be better architected and more reusable with minitest + D.I. rather than rspec.
I've not checked recently but last time I used it didn't provide colour output without plugins and didn't include verifying doubles or spies out of the box.
There were a lot of other decisions required to make Minitest plesant in non-rails projects.
You can still use dependency injection with Rspec, it's just a nicer experience IMHO.