怎样在Golang中模拟依赖进行测试 使用接口与mock技术的实战案例

package repository

import "errors"

// ErrUserNotFound 定义一个用户未找到的错误
var ErrUserNotFound = errors.New("user not found")

// User represents a user in the system.
type User struct {
    ID   string
    Name string
    Email string
}

// UserRepository 定义了用户数据存储的接口
type UserRepository interface {
    GetUserByID(id string) (*User, error)
    SaveUser(user *User) error
}

UserRepository

package service

import (
    "fmt"
    "your_module_path/repository" // 替换为你的模块路径
)

// UserService handles user-related business logic.
type UserService struct {
    repo repository.UserRepository
}

// NewUserService creates a new UserService.
func NewUserService(repo repository.UserRepository) *UserService {
    return &UserService{repo: repo}
}

// GetUserDetails retrieves user details by ID.
func (s *UserService) GetUserDetails(userID string) (string, error) {
    user, err := s.repo.GetUserByID(userID)
    if err != nil {
        if err == repository.ErrUserNotFound {
            return "", fmt.Errorf("user %s not found", userID)
        }
        return "", fmt.Errorf("failed to get user details: %w", err)
    }
    return fmt.Sprintf("User ID: %s, Name: %s, Email: %s", user.ID, user.Name, user.Email), nil
}

// CreateUser creates a new user.
func (s *UserService) CreateUser(user *repository.User) error {
    if err := s.repo.SaveUser(user); err != nil {
        return fmt.Errorf("failed to save user: %w", err)
    }
    return nil
}

UserService

UserRepository

package service_test

import (
    "errors"
    "testing"
    "your_module_path/repository" // 替换为你的模块路径
    "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) (*repository.User, error)
    SaveUserFunc    func(user *repository.User) error
}

// GetUserByID 实现 MockUserRepository 的 GetUserByID 方法
func (m *MockUserRepository) GetUserByID(id string) (*repository.User, error) {
    if m.GetUserByIDFunc != nil {
        return m.GetUserByIDFunc(id)
    }
    return nil, errors.New("GetUserByID not implemented in mock")
}

// SaveUser 实现 MockUserRepository 的 SaveUser 方法
func (m *MockUserRepository) SaveUser(user *repository.User) error {
    if m.SaveUserFunc != nil {
        return m.SaveUserFunc(user)
    }
    return errors.New("SaveUser not implemented in mock")
}

func TestUserService_GetUserDetails(t *testing.T) {
    tests := []struct {
        name         string
        userID       string
        mockRepoFunc func(id string) (*repository.User, error)
        expected     string
        expectError  bool
    }{
        {
            name:   "Successful retrieval",
            userID: "123",
            mockRepoFunc: func(id string) (*repository.User, error) {
                return &repository.User{ID: "123", Name: "Alice", Email: "alice@example.com"}, nil
            },
            expected:    "User ID: 123, Name: Alice, Email: alice@example.com",
            expectError: false,
        },
        {
            name:   "User not found",
            userID: "404",
            mockRepoFunc: func(id string) (*repository.User, error) {
                return nil, repository.ErrUserNotFound
            },
            expected:    "",
            expectError: true,
        },
        {
            name:   "Database error",
            userID: "500",
            mockRepoFunc: func(id string) (*repository.User, error) {
                return nil, errors.New("database connection failed")
            },
            expected:    "",
            expectError: true,
        },
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            mockRepo := &MockUserRepository{
                GetUserByIDFunc: tt.mockRepoFunc,
            }
            userService := service.NewUserService(mockRepo)

            details, err := userService.GetUserDetails(tt.userID)

            if tt.expectError {
                if err == nil {
                    t.Errorf("Expected an error but got none")
                }
            } else {
                if err != nil {
                    t.Errorf("Did not expect an error but got: %v", err)
                }
                if details != tt.expected {
                    t.Errorf("Expected '%s', got '%s'", tt.expected, details)
                }
            }
        })
    }
}

func TestUserService_CreateUser(t *testing.T) {
    tests := []struct {
        name        string
        userToSave  *repository.User
        mockRepoFunc func(user *repository.User) error
        expectError bool
    }{
        {
            name: "Successful creation",
            userToSave: &repository.User{ID: "new", Name: "Bob", Email: "bob@example.com"},
            mockRepoFunc: func(user *repository.User) error {
                return nil // Simulate successful save
            },
            expectError: false,
        },
        {
            name: "Failed creation due to database error",
            userToSave: &repository.User{ID: "fail", Name: "Charlie", Email: "charlie@example.com"},
            mockRepoFunc: func(user *repository.User) error {
                return errors.New("database write error") // Simulate a database error
            },
            expectError: true,
        },
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            mockRepo := &MockUserRepository{
                SaveUserFunc: tt.mockRepoFunc,
            }
            userService := service.NewUserService(mockRepo)

            err := userService.CreateUser(tt.userToSave)

            if tt.expectError {
                if err == nil {
                    t.Errorf("Expected an error but got none")
                }
            } else {
                if err != nil {
                    t.Errorf("Did not expect an error but got: %v", err)
                }
            }
        })
    }
}

implements

MySQLRepository

PostgreSQLRepository

UserRepository

UserService

GetUserByID

SaveUser

UserService

gomock

MockUserRepository

gomock

gomock

gomock