Interface mocking tool for go generate.

By Mat Ryer and David Hernandez, with ideas lovingly stolen from Ernesto Jimenez.

Usage

In a command line:

moq InterfaceName -out mocks_test.go

In code (for go generate):

package my

//go:generate moq MyInterface -out myinterface_moq_test.go

type MyInterface interface {
	Method1() error
	Method2(i int)
}

Then run go generate for your package.

Install

go install github.com/matryer/moq

How to use it

Mocking interfaces is a nice way to write unit tests where you can easily control the behaviour of the mocked object.

Moq creates a struct that has a function field for each method, which you can declare in your test code.

This this example, Moq generated the EmailSenderMock type:

func TestCompleteSignup(t *testing.T) {

	called := false
	var sentTo string 

	mockedEmailSender = &EmailSenderMock{
		SendFunc: func(to, subject, body string) error {
			called = true
			sentTo = to
			return nil
		},
	}

	CompleteSignUp("me@email.com", mockedEmailSender)

	if called == false {
		t.Error("Sender.Send expected")
	}
	if sentTo != "me@email.com" {
		t.Errorf("unexpected recipient: %s", sentTo)
	}

}

func CompleteSignUp(to string, sender EmailSender) {
	// TODO: this
}

The mocked structure implements the interface, where each method calls the associated function field.

Tips

• Keep mocked logic inside the test that is using it
• Only mock the fields you need - it will panic if a nil function gets called
• Use closured variables inside your test function to capture details about the calls to the methods
• Use go:generate to invoke the moq command