收听以调用Golang中另一个结构使用的结构函数

Question

This question already has an answer here:

• How to mock a method call of a struct in test case at go 1 answer

So I am a beginner with mocking struct and functions in Golang. I basically want to check if a function has been called for unit testing purpose. Here is the code:

type A struct {

}

func (a *A) Foo (){}

type B struct {
    a *A
}

func (b* B) Bar () {
    a.Foo()
}

I basically want to check that Foo is indeed called when Bar is called

I know there is some mock framework available for Golang but they are pretty complicated when it comes to testing existing struct and struct methods

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Answer 1

If you want to test B and see if it really calls A's Foo function, you need to mock out the A object. Since the function you want to check for is Foo, just create a simple Fooer interface (which is what you would call it in Go, the function plus 'er') with only that function. Replace B's reference to A with one to Fooer and you are good. I created a little sample based on your code here on the Go Playground:

package main

import "testing"

type A struct {
}

func (a *A) Foo() {}

type Fooer interface {
    Foo()
}

type B struct {
    a Fooer
}

func (b *B) Bar() {
    b.a.Foo()
}

func main() {
    var a A
    var b B
    b.a = &a
    b.Bar()
}

// in your test:

type mockFooer struct {
    fooCalls int
}

func (f *mockFooer) Foo() {
    f.fooCalls++
}

func Test(t *testing.T) {
    var mock mockFooer
    var bUnderTest B
    bUnderTest.a = &mock
    bUnderTest.Bar()
    if mock.fooCalls != 1 {
        t.Error("Foo not called")
    }
}