英文:
How to mock db ping without sqlmock
问题
我想了解如何重构我的代码，使用mock.Mock来模拟db.Ping()。首先，我想先了解这个概念，而不使用框架。
这是我想要测试的代码：
func Connect() (*sql.DB, error) {db, err := sql.Open("mysql", "root:secret@tcp(s-maria-db)/s_db")if err != nil {return nil, err}for i := 0; i < 60; i++ {// 我希望模拟这部分if err := db.Ping(); err == nil {break}time.Sleep(time.Second)}return db, nil}
我尝试了这个帖子https://stackoverflow.com/questions/57723476/how-to-mock-a-ping-command，但它实际上没有回答我的问题。如果有答案，我不理解该解决方案如何适用于我的代码。
英文:
I would like to understand how to refactor my code to mock db.Ping() using mock.Mock for example. I would like to understand the concept without a framework first.
Here is the code I want to test:
func Connect() (*sql.DB, error) {db, err := sql.Open("mysql", "root:secret@tcp(s-maria-db)/s_db")if err != nil {return nil, err}for i := 0; i < 60; i++ {// I am hoping to mock this portionif err := db.Ping(); err == nil {break}time.Sleep(time.Second)}return db, nil}
I attempted this post https://stackoverflow.com/questions/57723476/how-to-mock-a-ping-command, but this has not actually answered the question. If it does, I do not understand the solution as it applies to my code.
答案1
得分: 1
你需要使用一个单独的函数来进行ping操作，并且它需要接受一个接口，这样你就可以有条件地传入一个真实的*sql.DB或者一个模拟对象。这是因为你不能在一个结构体上覆盖一个方法。
// Connect函数打开与数据库的连接。func Connect() (*sql.DB, error) {return sql.Open("mysql", "root:secret@tcp(s-maria-db)/s_db")}// Pinger定义了一个ping操作的接口。type Pinger interface {Ping() error}// Ping函数尝试对数据库进行ping操作，在失败之前尝试多次。func Ping(p Pinger) error {const maxAttempts = 60var err errorfor i := 0; i < maxAttempts; i++ {if err = p.Ping(); err == nil {return nil}if i < maxAttempts - 1 {time.Sleep(time.Second)}}return err}
func main() {if err := run(); err != nil {log.Fatal(err)}}func run() error {db, err := Connect()if err != nil {return fmt.Errorf("连接到数据库时出错：%w", err)}defer db.Close()if err = Ping(db); err != nil {return fmt.Errorf("ping数据库时出错：%w", err)}...}
type mockDB struct {mock.Mock}func (m *mockDB) Ping() error {args := m.Called()return args.Error(0)}func TestPing(t *testing.T) {db := &mockDB{}db.On("Ping").Return(...)err := Ping(db)...db.AssertExpectations(t)}
英文:
You need to use a separate function for pinging, and it needs to accept an interface so you can conditionally pass in a real *sql.DB or a mock. This is because you can't override a method on a struct.
// Connect opens a connection to the database.func Connect() (*sql.DB, error) {return sql.Open("mysql", "root:secret@tcp(s-maria-db)/s_db")}// Pinger defines an interface for pinging.type Pinger interface {Ping() error}// Ping attempts to ping the database, trying several times before failing.func Ping(p Pinger) error {const maxAttempts = 60var err errorfor i := 0; i < maxAttempts; i++ {if err = p.Ping(); err == nil {return nil}if i < maxAttempts - 1 {time.Sleep(time.Second)}}return err}
func main() {if err := run(); err != nil {log.Fatal(err)}}func run() error {db, err := Connect()if err != nil {return fmt.Errorf("connecting to db: %w", err)}defer db.Close()if err = Ping(db); err != nil {return fmt.Errorf("pinging db: %w", err)}...}
type mockDB struct {mock.Mock}func (m *mockDB) Ping() error {args := m.Called()return args.Error(0)}func TestPing(t *testing.T) {db := &mockDB{}db.On("Ping").Return(...)err := Ping(db)...db.AssertExpectations(t)}
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