Martian Proxy is a programmable HTTP proxy designed to be used for testing.
Martian is a great tool to use if you want to:
Verify that all (or some subset) of requests are secure
Mock external services at the network layer
Inject headers, modify cookies or perform other mutations of HTTP requests and responses
Verify that pingbacks happen when you think they should
Unwrap encrypted traffic (requires install of CA certificate in browser)
By taking advantage of Go cross-compilation, Martian can be deployed anywhere that Go can target.