Github.com/uber/mock

External

• https://pkg.go.dev/go.uber.org/mock/gomock

Internal

• Go Testing

Installation

mockgen Installation

https://github.com/uber-go/mock#installation

go install go.uber.org/mock/mockgen@latest

mockgen -version
v0.4.0

Import

import "go.uber.org/mock/gomock"

mockgen

Method 1 ("Package"):

To generate the mock code at stdout:

mockgen -package <name_of_the_package_mock_will_belong_to> <package_import_path> <InterfaceName>[,<InterfaceName>]

Once the source file is generated, you may need to replace gomock "github.com/golang/mock/gomock" with go.uber.org/mock/gomock.

Method 2 ("Source Mode"):

Navigate to the directory that contains the source code and:

mockgen -package <name_of_the_package_mock_will_belong_to> -source=myfile.go [InterfaceName]

Bazel Integration with the gomock Rule

https://github.com/jmhodges/bazel_gomock#use

Attributes

package

The package name to use in the generated output. See the gomock documentation on -package for more information.

library

The go_library to find the interfaces in.

out

The name of the generated source code file. The file will be written in the current directory.

Programming Model

Instantiate the Mock

import "go.uber.org/mock/gomock"

...

func TestSomething(t *testing.T) {
  mockController := gomock.NewController(t)
  mockSomething := mockgeneratedpkg.NewMockSomething(mockController)
  ...
}

Setup Expectations

Define the Behavior of a Method

Configuring a mock to handle a specific method call.

mockSomething.EXPECT().SomeMethod(gomock.Any(), "some specific value").Return("some other value")

Note that if the method is not called at the end of the test, the mock will fail the test with:

missing call(s) to *mock_pkg.MockSomething.SomeMethod(...)
aborting test due to missing call(s)