Package spies provides a testing spy framework for Go.
It is heavily influenced by
(testify/mock.)[https://github.com/stretchr/testify#mock-package]
Roughly speaking,
you implement an interface against a spy,
then you can use the internal Spy object to record
responses to return,
and then assert calls against the spy.
Why this package and not testify/mock?
I personally find that Spies are more flexbile,
and encourage you to actually test the things
that need to be tested.
For instance,
often a test double needs to return
a value in response to a query
(e.g. wehave.HowManyBananas() returns 0).
If the code under test changes
and no longer needs to make that query,
there's no reason that the tests should break.
It'd be keen to have code generation for spies, since they wind up usually being very standard structures. However, I've often found it handy to extend from the basic patterns with little utility methods on the control struct.
It might also be nice to have a few extra methods related to selecting and inspecting calls, since that can get a little hairy.