assert VS counterfeiter

https://github.com/alecthomas/assert As an assertion library

then just replace whole function, don't generate manually the mock '__') or it would get out of hand fast, you can just use codegen that static typed like https://github.com/maxbrunsfeld/counterfeiter

Yes, that's a good way to do that; there are a lot of packages that allow you to mock and spy the calls if you're looking for one that generates the code for you I can recommend counterfeiter, I also have a short blog that covers it.

I prefer https://github.com/maxbrunsfeld/counterfeiter

counterfeiter is another tool, it creates mocks, stubs and spies; here is a short blog I wrote covering it.

for dependency injection I suggest you use https://github.com/maxbrunsfeld/counterfeiter, but if you using really fast database (that can spawn fast using docker and has fast trx/sec) you can use it directly without dependency injection with https://github.com/ory/dockertest

Agree with u/mmknightx there is a tool that assist in creating fake or mock classes for your interfaces https://github.com/maxbrunsfeld/counterfeiter

Another alternative to use would be counterfeiter, it generates a type from your interface that could be used as a mock, stub or spy. I wrote a short post covering that tool if you're interested.