How to write mock for structs in Go

Question

I want to write unit test for a function Hirethat will require ridicule CarFactoryand Carstructs. See the following code:

package main

type Car struct {
    Name string
}

func (h Car) Run() { ... }

type CarFactory struct {}

func (e CarFactory) MakeCar() Car {
    return Car{}
}

func Transport(cf CarFactory) {
    ...
    car := cf.MakeCar()
    car.Run()
    ...
}

In other OOP languages, such as Java, C # or C ++, I can simply define CarFactoryMockand CarMockthat extend CarFactoryand Carthen override the method MakeCar()to return the objectCarMock

class CarMock extends Car {
    public Run() {...}
}

class CarFactoryMock extends CarFactory {
    public Car MakeCar() { return new CarMock(); }                                                                                                                                                                                        
}

Transport(new CarFactoryMock())

How to achieve this in Go?

Please note that I can modify the prototype and source code function Transport, but must keep the tags CarFactoryand Carthe same as they are taken from the third package

---

The last piece of code was about the Man and the Employee, which leads to confusion`.

Answer 1

. Go , , .

,

type Car struct {
    Name string
}

func (c Car) Run() { 
    fmt.Println("Real car " + c.Name + " is running")
}

type CarFactory struct {}

func (cf CarFactory) MakeCar(name string) Car {
    return Car{name}
}

Go , Transport struct.

type ICar interface {
    Run()
}

type ICarFactory interface {
    MakeCar(name string) ICar
}

func Transport(cf ICarFactory) {
    ...
    car := cf.MakeCar("lamborghini")
    car.Run()
    ...
}

type CarMock struct {
    Name string
}

func (cm CarMock) Run() {
    fmt.Println("Mocking car " + cm.Name + " is running")
}

type CarFactoryMock struct {}
func (cf CarFactoryMock) MakeCar(name string) ICar {
    return CarMock{name}
}

Transport(CarFactoryMock{}). Transport (CarFactory {}), go

cannot use CarFactory literal (type CarFactory) as type ICarFactory in argument to Transport:
    CarFactory does not implement ICarFactory (wrong type for MakeCar method)
        have MakeCar(string) Car
        want MakeCar(string) ICar

, MakeCar ICar MakeCar Car. . , , Car ICar.

type CarFactoryWrapper struct {
    CarFactory
}

func (cf CarFactoryWrapper) MakeCar(name string) ICar {
    return cf.CarFactory.MakeCar(name)
}

Transport(CarFactoryWrapper{CarFactory{}})

https://play.golang.org/p/6YyeZP4tcC

Answer 2

.

type Employee interface {
    GetHuman() Human
}

type RealEmployee struct {
    Company string
    h Human
}

func (e RealEmployee) GetHuman() Human {
    return e.h
}

// Call Hire with real employee
Hire(RealEmployee{h: RealHuman})

Hire Employee, MockEmployee .

func Hire(e Employee) {
    ...
    h := e.GetHuman()
    fmt.Println(h.Name)
    ...
}

// Mock Employee instance
type MockEmployee struct {
    Company string
    h Human
}

func (m MockEmployee) GetHuman() Human {
    return m.h
}

// Call Hire to test with mock employee
Hire(MockEmployee{h: MockHuman})