WebMock

Supports over 10 popular Ruby HTTP clients including Net::HTTP, HTTParty, and Excon, as listed in the README, ensuring broad compatibility without switching libraries.

Matches requests by method, URI (with regex and RFC 6570 templates), headers, and body (JSON, XML, etc.), demonstrated in examples like stubbing with partial hashes or lambda blocks.

Out-of-the-box support for RSpec, MiniTest, and Test::Unit with simple require statements, as shown in setup instructions for each framework.

Allows custom responses, errors, timeouts, and Rack app delegation, with features like chained responses and dynamic evaluation from blocks or lambdas.