Golang测试中模拟依赖对象实践

package service

import (
    "errors"
    "fmt"
)

// 定义用户模型
type User struct {
    ID   string
    Name string
    Email string
}

// 定义用户仓库接口
type UserRepository interface {
    GetUserByID(id string) (*User, error)
    // 可以有更多方法，比如 SaveUser, DeleteUser等
}

// UserService 依赖 UserRepository
type UserService struct {
    repo UserRepository
}

// NewUserService 创建 UserService 实例
func NewUserService(repo UserRepository) *UserService {
    return &UserService{repo: repo}
}

// GetUserDetail 获取用户详情
func (s *UserService) GetUserDetail(userID string) (string, error) {
    user, err := s.repo.GetUserByID(userID)
    if err != nil {
        return "", fmt.Errorf("failed to get user: %w", err)
    }
    if user == nil {
        return "", errors.New("user not found")
    }
    return fmt.Sprintf("User ID: %s, Name: %s, Email: %s", user.ID, user.Name, user.Email), nil
}

UserService.GetUserDetail

UserRepository

package service_test

import (
    "errors"
    "testing"

    "your_module_path/service" // 替换为你的模块路径
)

// MockUserRepository 是 UserRepository 接口的模拟实现
type MockUserRepository struct {
    GetUserByIDFunc func(id string) (*service.User, error)
}

// GetUserByID 实现了 UserRepository 接口的方法
func (m *MockUserRepository) GetUserByID(id string) (*service.User, error) {
    if m.GetUserByIDFunc != nil {
        return m.GetUserByIDFunc(id)
    }
    // 默认行为，如果未设置则返回nil
    return nil, nil
}

func TestUserService_GetUserDetail(t *testing.T) {
    t.Run("用户存在时应返回正确详情", func(t *testing.T) {
        expectedUser := &service.User{ID: "123", Name: "Alice", Email: "alice@example.com"}
        mockRepo := &MockUserRepository{
            GetUserByIDFunc: func(id string) (*service.User, error) {
                if id == "123" {
                    return expectedUser, nil
                }
                return nil, errors.New("user not found") // 模拟其他ID找不到
            },
        }

        userService := service.NewUserService(mockRepo)
        detail, err := userService.GetUserDetail("123")

        if err != nil {
            t.Errorf("Expected no error, got %v", err)
        }
        expectedDetail := "User ID: 123, Name: Alice, Email: alice@example.com"
        if detail != expectedDetail {
            t.Errorf("Expected detail %q, got %q", expectedDetail, detail)
        }
    })

    t.Run("用户不存在时应返回用户未找到错误", func(t *testing.T) {
        mockRepo := &MockUserRepository{
            GetUserByIDFunc: func(id string) (*service.User, error) {
                return nil, nil // 模拟仓库返回nil表示用户不存在
            },
        }
        userService := service.NewUserService(mockRepo)
        _, err := userService.GetUserDetail("nonexistent")

        if err == nil {
            t.Errorf("Expected error for non-existent user, got nil")
        }
        if err.Error() != "user not found" {
            t.Errorf("Expected error 'user not found', got %q", err.Error())
        }
    })

    t.Run("仓库返回错误时应传递错误", func(t *testing.T) {
        mockRepo := &MockUserRepository{
            GetUserByIDFunc: func(id string) (*service.User, error) {
                return nil, errors.New("database connection failed") // 模拟数据库错误
            },
        }
        userService := service.NewUserService(mockRepo)
        _, err := userService.GetUserDetail("123")

        if err == nil {
            t.Errorf("Expected error from repository, got nil")
        }
        if err.Error() != "failed to get user: database connection failed" {
            t.Errorf("Expected error 'failed to get user: database connection failed', got %q", err.Error())
        }
    })
}

MockUserRepository

// 假设 UserRepository 只有一个 GetUserByID 方法，或者我们只关心这一个
type MockGetUserByIDFunc func(id string) (*service.User, error)

func (f MockGetUserByIDFunc) GetUserByID(id string) (*service.User, error) {
    return f(id)
}

// 在测试中使用
func TestUserService_GetUserDetail_FuncMock(t *testing.T) {
    mockRepo := MockGetUserByIDFunc(func(id string) (*service.User, error) {
        if id == "456" {
            return &service.User{ID: "456", Name: "Bob"}, nil
        }
        return nil, errors.New("not found")
    })

    userService := service.NewUserService(mockRepo) // 直接传入函数类型
    detail, err := userService.GetUserDetail("456")
    // ... 断言 ...
}

testify/mock