RR

RR supports stubs, mocks, spies, proxies, and class instance doubles, providing a wide range of techniques for isolating dependencies, as detailed in the whirlwind tour.

The syntax minimizes boilerplate, with concise calls like `stub(object).foo` and `mock.proxy(MyClass).new`, emphasizing readability and speed in test writing.

It works seamlessly with RSpec, Test::Unit, MiniTest, and Minitest, allowing developers to use the same double techniques across different testing environments without major configuration changes.

Unique among Ruby mocking libraries, proxies let you intercept existing methods to modify return values while preserving original behavior, useful for complex test scenarios as shown in the examples.