Depends on the API and how much testing you need. You want to test your code, not the API's availability or correctness. But it can be as easy as using a fake

Depends on the API and how much testing you need. You want to test your code, not the API's availability or correctness. But it can be as easy as using a fake http library and mocking the responses, or using a httptest server: https://onsi.github.io/gomega/#ghttp-testing-http-clients https://onsi.github.io/gomega/#ghttp-testing-http-clients If the API is complicated and you have to write your own fake server, that might not make sense for small projects.