Mocktail is a mocking library for Ruby built with modern Ruby 3 APIs and the only one with first-class support for type checking with Sorbet. Mocktail was created to accelerate test-driven development in Ruby and is designed to prevent common problems that lead to brittle and confusing tests.
Your first choice is a consequential one: how do you want your Mocktail?
You can also skip all the fun stuff and dive straight into the full API documentation.