具有ORM交互的单元测试Go函数

Question

I have written a function:

func AllItems(w http.ResponseWriter, r *http.Request) {
    db, err := gorm.Open("sqlite3", "test.db")
    if err != nil {
        panic("failed to connect database")
    }
    defer db.Close()

    var items [] Item
    db.Find(&items)
    fmt.Println("{}", items)

    json.NewEncoder(w).Encode(items)
}

I want to do unit testing on this. Ideally, unit testing means that each line of the function needs to be tested. I'm not sure how I should test if a database connection is opened and then if it is displaying all the contents of the database. How should I test this code?

This function is the GET endpoint of a simple CRUD application. The code is here.

Answer 1

Refactor your code and break it down into smaller, testable functions which you pass dependencies to. Also create interfaces for the dependencies to make testing easier.

For example:

type myDatabaseInterface interface {
    Find(interface{}) // this signature should match the real db.Find()
}

func AllItems(w http.ResponseWriter, r *http.Request) {
    db, err := gorm.Open("sqlite3", "test.db")
    if err != nil {
        panic("failed to connect database")
    }
    defer db.Close()
    items := findItems(db)
    json.NewEncoder(w).Encode(items)
}

func find(db myDatabaseInterface) ([]Item) {
    var items []Item
    db.Find(&items)
    return items
}

Then you can create mocks for your dependencies and use them in your tests:

type mock struct {}

// mock should implement myDatabaseInterface to be able to pass it to the function
func (m *mock) Find(interface{}) {
    // implement the mock to satisfy your test
}

func Test_find(t *testing.T) {
    m := mock{}
    res := find(m)
    // do testing
}

Instead of calling Open every time you handle a request maybe you should open it outside and have it available to your function. That way the handler becomes so small there's no need to test it really:

func makeAllItemsHandler(db myDatabaseInterface) func(http.ResponseWriter, *http.Request) {
    return func(http.ResponseWriter, *http.Request) {
        items := findItems(db)
        json.NewEncoder(w).Encode(items)
    }
}

Then you can create a db once and for all when you set up your application and pass it to the functions that need it thus removing hard to test code from the functions.