An example that shows the use of test doubles, ie. fakes and mocks, in Go unit testing.
Fake and mock are collectively called test doubles.
- Fake - Fake doesn't modify the behavior of the system under test. There are 2 forms of fakes:
- Fake data - Use non-real (fake) data eg. [email protected]
- Fake system - Instead of using an actual system dependency in production, eg. Postgres or MySQL, the test suite uses a simpler system, eg. simple SQLite, to mimic the actual system.
- Mock - You have components in your system that call or depend on another dependency. A mock allows the tester to mock that dependency and assert that your system has interacted with the dependency. This recipe provides examples for 2 popular mock frameworks:
- Gomock - This is a framework that generates mock code at build time.
- Testify Mock - This is a framework that relies on reflection to generate mocks at runtime.
Read here for an explanation on fake vs mock.
This example is based on a forgot password web service, which generates a random password and replaces the existing password in the system. The main components are:
- Account - The representation of the user's account in the system.
- AccountModel - The data access layer that creates, fetches, and deletes a user's account.
- AccountService - The API endpoint, from which the user can call to reset his/her password.
In unit test api_test.go, we see that the test is using both a fake and mock:
- Test using a fake - We emulate data access to a SQL database with in-code
mapdata type. Note: it probably more relevant using SQLite to fake the SQL database access layer than Golangmap - Test using a mock - We mock the
AcccountModelwith MockAccountModel.
-
Install mockgen
$ make install
-
Generate the mocks.
$ make mockgen
-
Run the test
$ go test -v ./api -
Alternatively, just run everything with the following command:
$ make install # Optional: run this if you haven't installed mockgen $ make # Run all the above commands