使用Gomock设置模拟函数返回值

gw.EXPECT().GetQuestionById(1)

package main

import (
    "fmt"
    "testing"

    "github.com/golang/mock/gomock"
)

// 假设我们有一个这样的接口
type QuestionService interface {
    GetQuestionById(id int) Question
}

// 接口的实现（在实际项目中可能是一个数据库或RPC客户端）
type RealQuestionService struct{}

func (s *RealQuestionService) GetQuestionById(id int) Question {
    // 实际业务逻辑，这里简化
    return Question{ID: id, Content: fmt.Sprintf("Real Question %d", id)}
}

// 定义一个Question结构体
type Question struct {
    ID      int
    Content string
}

// 模拟接口的实现
// mock_question_service.go (由mockgen生成)
// type MockQuestionService struct {
//  ctrl     *gomock.Controller
//  recorder *MockQuestionServiceMockRecorder
// }
// func NewMockQuestionService(ctrl *gomock.Controller) *MockQuestionService { ... }
// func (m *MockQuestionService) GetQuestionById(arg0 int) Question { ... }
// type MockQuestionServiceMockRecorder struct { ... }
// func (mr *MockQuestionServiceMockRecorder) GetQuestionById(arg0 interface{}) *gomock.Call { ... }

func TestGetQuestionByIdWithMock(t *testing.T) {
    // 1. 创建gomock控制器
    ctrl := gomock.NewController(t)
    defer ctrl.Finish() // 确保在测试结束时调用ctrl.Finish()

    // 2. 创建模拟对象
    // 假设MockQuestionService是由mockgen工具根据QuestionService接口生成的
    // 这里我们直接使用一个假设的模拟对象，实际中会是NewMockQuestionService(ctrl)
    mockService := NewMockQuestionService(ctrl) // 请替换为实际生成的mock对象构造函数

    // 3. 定义预期调用并设置返回值
    expectedQuestion := Question{ID: 1, Content: "Foo Bar Question"}
    mockService.EXPECT().GetQuestionById(1).Return(expectedQuestion)

    // 4. 调用业务逻辑（这里直接调用模拟对象的方法来演示）
    // 在实际的单元测试中，你可能会调用一个依赖于QuestionService的SUT（System Under Test）方法
    result := mockService.GetQuestionById(1)

    // 5. 断言结果
    if result.ID != expectedQuestion.ID || result.Content != expectedQuestion.Content {
        t.Errorf("Expected question %v, got %v", expectedQuestion, result)
    }
    fmt.Printf("Mocked GetQuestionById(1) returned: %+v\n", result)

    // 尝试调用未预期的参数，会导致测试失败 (gomock.Controller.Finish()会检查)
    // mockService.GetQuestionById(2) // 这行如果执行，且没有对应的EXPECT，会在ctrl.Finish()时报错
}

// 为了让上面的示例代码能够运行，我们需要一个NewMockQuestionService的定义
// 实际中，这个会由mockgen工具生成。这里提供一个简化版以供演示。
type MockQuestionService struct {
    ctrl     *gomock.Controller
    recorder *MockQuestionServiceMockRecorder
}

func NewMockQuestionService(ctrl *gomock.Controller) *MockQuestionService {
    mock := &MockQuestionService{ctrl: ctrl}
    mock.recorder = &MockQuestionServiceMockRecorder{mock}
    return mock
}

type MockQuestionServiceMockRecorder struct {
    mock *MockQuestionService
}

func (mr *MockQuestionServiceMockRecorder) GetQuestionById(arg0 interface{}) *gomock.Call {
    mr.mock.ctrl.T.Helper()
    call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetQuestionById", reflect.TypeOf((*QuestionService)(nil)).Elem().Method(0), arg0)
    return call
}

func (m *MockQuestionService) GetQuestionById(id int) Question {
    m.ctrl.T.Helper()
    ret := m.ctrl.Call(m, "GetQuestionById", id)
    return ret[0].(Question)
}

// 引入reflect包以支持RecordCallWithMethodType
import "reflect"