fake-mock

Fake vs Mock

An example that shows the use of test doubles, ie. fakes and mocks, in Go unit testing.

Definition

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. nobody@example.com
  • 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.

Project Description

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 map data type. Note: it probably more relevant using SQLite to fake the SQL database access layer than Golang map
• Test using a mock - We mock the AcccountModel with MockAccountModel.

Setup

1. Install mockgen

   $ make install
   

2. Generate the mocks.

   $ make mockgen
   

3. Run the test

   $ go test -v ./api
   

4. 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
   

Reference

• GoMock
• Stretchr Testify mock package