httpmock VS testfixtures

We will use httpmock for this purpose. Inside function setupSuite(), where we created useCase and provided nil as a billingClient now we will pass mocked http client:

Alternatively, you could use an http mock library like https://github.com/jarcoal/httpmock, and override the urls the RealClient calls with a mock response in your tests.

To mock an API: https://github.com/jarcoal/httpmock to use when your code calls external APIs so you don't want your tests call the real API. No need to create an interface as you do.

I'm the author of https://github.com/go-testfixtures/testfixtures, a library written to make it easier to write tests with a real database and test data. You might want to use it together with docker-compose, for example.

To solve the problem we will use testfixtures. Create a folders fixtures и fixtures/storage and put a file users.yaml inside:

A lot of good suggestions here, I would also take a look at go-testfixtures which allows you to create some simple yaml-based fixture data to use with unit testing. It's quick and easy, but yes can get unwieldy the more you add.

I built an alternative to Make written in Go that is simpler to use and cross-platform: https://taskfile.dev/

Also, a library to write tests with databases for Go: https://github.com/go-testfixtures/testfixtures