如何模拟在 Go 中将结果写入其参数的函数

Question

我正在通过https://github.com/stretchr/testify在 golang 中编写单元测试 假设我有以下方法，func DoSomething(result interface{}) error {    // write some data to result    return nil}所以调用者可以调用DoSomething如下result := &SomeStruct{}err := DoSomething(result)if err != nil {  fmt.Println(err)} else {  fmt.Println("The result is", result)}现在我知道如何使用testify或其他一些模拟工具来模拟返回值（它在err这里），比如mockObj.On("DoSomething", mock.Anything).Return(errors.New("mock error"))result我的问题是在这种情况下“我如何模拟论点”？由于result不是返回值而是参数，调用者通过传递一个结构的指针来调用它，函数对其进行修改。

Answer 1

您可以使用以下(*Call).Run方法：

Run 设置在返回之前调用的处理程序。它可以在模拟一个方法（例如解组器）时使用，该方法接受一个指向结构的指针并在该结构中设置属性

例子：

mockObj.On("Unmarshal", mock.AnythingOfType("*map[string]interface{}")).Return().Run(func(args Arguments) {

    arg := args.Get(0).(*map[string]interface{})

    arg["foo"] = "bar"

})

Answer 2

services/message.go：

type messageService struct {

    HttpClient http.Client

    BaseURL    string

}

func (m *messageService) MarkAllMessages(accesstoken string) []*model.MarkedMessage {

    endpoint := m.BaseURL + "/message/mark_all"

    var res model.MarkAllMessagesResponse

    if err := m.HttpClient.Post(endpoint, &MarkAllMessagesRequestPayload{Accesstoken: accesstoken}, &res); err != nil {

        fmt.Println(err)

        return res.MarkedMsgs

    }

    return res.MarkedMsgs

}

我们传递res给m.HttpClient.Post方法。在此方法中，res将填充json.unmarshal方法。

mocks/http.go：

package mocks

import (

    "io"

    "github.com/stretchr/testify/mock"

)

type MockedHttp struct {

    mock.Mock

}

func (m *MockedHttp) Get(url string, data interface{}) error {

    args := m.Called(url, data)

    return args.Error(0)

}

func (m *MockedHttp) Post(url string, body interface{}, data interface{}) error {

    args := m.Called(url, body, data)

    return args.Error(0)

}

services/message_test.go：

package services_test

import (

    "errors"

    "reflect"

    "strconv"

    "testing"

    "github.com/stretchr/testify/mock"

    "github.com/mrdulin/gqlgen-cnode/graph/model"

    "github.com/mrdulin/gqlgen-cnode/services"

    "github.com/mrdulin/gqlgen-cnode/mocks"

)

const (

    baseURL     string = "http://localhost/api/v1"

    accesstoken string = "123"

)

func TestMessageService_MarkAllMessages(t *testing.T) {

    t.Run("should mark all messaages", func(t *testing.T) {

        testHttp := new(mocks.MockedHttp)

        var res model.MarkAllMessagesResponse

        var markedMsgs []*model.MarkedMessage

        for i := 1; i <= 3; i++ {

            markedMsgs = append(markedMsgs, &model.MarkedMessage{ID: strconv.Itoa(i)})

        }

        postBody := services.MarkAllMessagesRequestPayload{Accesstoken: accesstoken}

        testHttp.On("Post", baseURL+"/message/mark_all", &postBody, &res).Return(nil).Run(func(args mock.Arguments) {

            arg := args.Get(2).(*model.MarkAllMessagesResponse)

            arg.MarkedMsgs = markedMsgs

        })

        service := services.NewMessageService(testHttp, baseURL)

        got := service.MarkAllMessages(accesstoken)

        want := markedMsgs

        testHttp.AssertExpectations(t)

        if !reflect.DeepEqual(got, want) {

            t.Errorf("got wrong return value. got: %#v, want: %#v", got, want)

        }

    })

    t.Run("should print error and return empty slice", func(t *testing.T) {

        var res model.MarkAllMessagesResponse

        testHttp := new(mocks.MockedHttp)

        postBody := services.MarkAllMessagesRequestPayload{Accesstoken: accesstoken}

        testHttp.On("Post", baseURL+"/message/mark_all", &postBody, &res).Return(errors.New("network"))

        service := services.NewMessageService(testHttp, baseURL)

        got := service.MarkAllMessages(accesstoken)

        var want []*model.MarkedMessage

        testHttp.AssertExpectations(t)

        if !reflect.DeepEqual(got, want) {

            t.Errorf("got wrong return value. got: %#v, want: %#v", got, want)

        }

    })

}

在单元测试用例中，我们填充了res# Call.Run方法并将返回值（res.MarkedMsgs）分配service.MarkAllMessages(accesstoken)给got变量。

单元测试结果和覆盖率：

=== RUN   TestMessageService_MarkAllMessages

--- PASS: TestMessageService_MarkAllMessages (0.00s)

=== RUN   TestMessageService_MarkAllMessages/should_mark_all_messaages

    TestMessageService_MarkAllMessages/should_mark_all_messaages: message_test.go:39: PASS: Post(string,*services.MarkAllMessagesRequestPayload,*model.MarkAllMessagesResponse)

    --- PASS: TestMessageService_MarkAllMessages/should_mark_all_messaages (0.00s)

=== RUN   TestMessageService_MarkAllMessages/should_print_error_and_return_empty_slice

network

    TestMessageService_MarkAllMessages/should_print_error_and_return_empty_slice: message_test.go:53: PASS: Post(string,*services.MarkAllMessagesRequestPayload,*model.MarkAllMessagesResponse)

    --- PASS: TestMessageService_MarkAllMessages/should_print_error_and_return_empty_slice (0.00s)

PASS

coverage: 5.6% of statements in ../../gqlgen-cnode/...

Process finished with exit code 0