如何在diff实现中使用函数接口

Question

Im using interface which I want to mock one method in it function1 in test and I wasn't able to figure it out how is the best to do it that for prod code it will provide 1 value and for test provide some mock value , can someone please give example ? (edited) this is the code:

https://play.golang.org/p/w367IOjADFV

package main

import (
    "fmt"
    "time"
)

type vInterface interface {
    function1() bool
}

type mStruct struct {
    info string
    time time.Time
}

func (s *mStruct) function1() bool {
    return true
}

func callSomething(si vInterface) bool {
    return si.function1()
}

func (s *mStruct) vl1() bool {
    s.time = time.Now()
    s.info = "vl1->info"
    return callSomething(s)
}

var currentVt1 mStruct

func main() {
    vl1 := currentVt1.vl1()

    fmt.Println(vl1)
}

The test is like this

func Test_callSomething(t *testing.T) {
    type args struct {
        si vInterface
    }
    tests := []struct {
        name string
        args args
        want bool
    }{
        {
            name: "my tests",
            args: args{

            },
            want: false,
        },
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            if got := callSomething(tt.args.si); got != tt.want {
                t.Errorf("callSomething() = %v, want %v", got, tt.want)
            }
        })
    }
}

But not sure how to mock it right ...

update

func Test_mStruct_vl1(t *testing.T) {
    type fields struct {
        info string
        time time.Time
    }
    tests := []struct {
        name   string
        fields fields
        want   bool
    }{
        {
            name: "some test",
            fields: struct {
                info string
                time time.Time
            }{info: "myinfo", time: time.Now() },

        },
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            s := &mStruct{
                info: tt.fields.info,
                time: tt.fields.time,
            }
            if got := s.vl1(); got != tt.want {
                t.Errorf("vl1() = %v, want %v", got, tt.want)
            }
        })
    }
}

Answer 1

First you need a type (any type) that implements the vInterface interface. Here's a simple example:

type mockedVInterface struct {
    value bool
}

func (m mockedVInterface) function1() bool {
    return m.value
}

This is a simple enough implementation which we can control: we can tell what its function1() function should return by simply setting that value to its value field.

This mockedVInterface type is created solely for testing purposes, the production code does not need it. Put it in the same file where you have the test code (put it before Test_callSomething()).

And here's the testing code:

func Test_callSomething(t *testing.T) {
    type args struct {
        si vInterface
    }
    tests := []struct {
        name string
        args args
        want bool
    }{
        {
            name: "testing false",
            args: args{
                si: mockedVInterface{value: false},
            },
            want: false,
        },
        {
            name: "testing true",
            args: args{
                si: mockedVInterface{value: true},
            },
            want: true,
        },
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            if got := callSomething(tt.args.si); got != tt.want {
                t.Errorf("callSomething() = %v, want %v", got, tt.want)
            }
        })
    }
}

Note that in this simple case we could also use a simple non-struct type that has bool as its underlying type like this:

type mockedVInterface bool

func (m mockedVInterface) function1() bool {
    return bool(m)
}

And it works and testing code is also simpler:

tests := []struct {
        name string
        args args
        want bool
    }{
        {
            name: "testing false",
            args: args{
                si: mockedVInterface(false),
            },
            want: false,
        },
        {
            name: "testing true",
            args: args{
                si: mockedVInterface(true),
            },
            want: true,
        },
    }

But this only works if the mockable interface has a single function with a single return value. In the general case a struct is needed.