单元测试框架示例 - 初学者指南

单元测试是确保代码在不同情况下正确运行的重要组成部分。本文通过一个简单的 todo 应用程序示例，指导初学者进行单元测试。首先，文章介绍了 Go 语言中 HTTP 请求处理程序的结构，包括 todo 模型和处理程序函数。然后，它展示了如何使用 net/http/httptest 包编写一个测试函数，该函数模拟 HTTP 请求并断言响应状态和内容。最后，文章强调了使用局部变量来存储状态以避免全局变量的问题，并提供了一个使用 app 结构来管理状态的示例。

这是我的 todo 应用程序的基本结构，称为“main.go”；

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "github.com/gorilla/mux"
)

//  todo struct (model)
type todo struct {
    id        string `json:"id"`
    task      string `json:"task"`
    completed bool   `json:"completed"`
}

var todos []todo

//  get all todos
func gettodos(w http.responsewriter, r *http.request) {
    w.header().set("content-type", "application/json")
    json.newencoder(w).encode(todos)
}

func main() {
    // init router
    r := mux.newrouter()

    // mock data
    todos = append(todos, todo{id: "1", task: "firsttask", completed: false})
    todos = append(todos, todo{id: "2", task: "secondtask", completed: false})

    fmt.println("go dude dude go ")

    r.handlefunc("/", func(w http.responsewriter, r *http.request) {
        fmt.fprint(w, "hello dudes")
    })

    r.handlefunc("/api/todos", gettodos).methods("get")

    log.fatal(http.listenandserve(":8080", r))
}

这是我的“main_test.go”

package main

import (
    "net/http"
    "net/http/httptest"
    "testing"
)

func testgettodos(t *testing.t) {
    req, err := http.newrequest("get", "/api/todos", nil)
    if err != nil {
        t.fatal(err)
    }
    rr := httptest.newrecorder()
    handler := http.handlerfunc(gettodos)
    handler.servehttp(rr, req)
    if status := rr.code; status != http.statusok {
        t.errorf("handler returned wrong status code: got %v want %v",
            status, http.statusok)
    }

    // check the response body is what we expect.
    expected := `[{id: "1", task: "firsttask", completed: false},{id: "2", task: "secondtask", completed: false}]`
    if rr.body.string() != expected {
        t.errorf("handler returned unexpected body: got %v want %v",
            rr.body.string(), expected)
    }
}

问题就在这里，我不断收到以下错误；

--- FAIL: TestGetTodos (0.00s)
    main_test.go:25: handler returned unexpected body: got null
         want [{Id: "1", Task: "FirstTask", Completed: false},{Id: "2", Task: "SecondTask", Completed: false}]
FAIL
exit status 1
FAIL   ..filesPath/backend   0.213s

我确实错过了如此简单的事情，但无法弄清楚。

解决方案

当您运行测试时，main 永远不会被调用，因此 todos 为空。

var todos []todo

这就是为什么 rr.body.string() 返回 null

如果您将模拟数据生成代码移至您正在测试的 gettodos 函数中

var todos []todo

//  get all todos
func gettodos(w http.responsewriter, r *http.request) {
    w.header().set("content-type", "application/json")
    var mocktodos []todo
    mocktodos = append(mocktodos, todo{id: "1", task: "firsttask", completed: false})
    mocktodos = append(mocktodos, todo{id: "2", task: "secondtask", completed: false})
    json.newencoder(w).encode(mocktodos)
}

测试仍然会失败，但主体将不再为空，而是显示

=== run   testgettodos
testgettodos: main_test.go:25: handler returned unexpected body: got [{"id":"1","task":"firsttask","completed":false},{"id":"2","task":"secondtask","completed":false}]
     want [{id: "1", task: "firsttask", completed: false},{id: "2", task: "secondtask", completed: false}]
--- fail: testgettodos (0.00s)
fail

那是因为你的期望不是正确的 json 格式。如果你更换

expected := `[{id: "1", task: "firsttask", completed: false},{id: "2", task: "secondtask", completed: false}]`

与

expected := "[{\"id\":\"1\",\"task\":\"firsttask\",\"completed\":false},{\"id\":\"2\",\"task\":\"secondtask\",\"completed\":false}]\n"

这将帮助您通过测试。

我在预期字符串的末尾添加了换行符 \n 因为 json.newencoder(w).encode(todos) 在输出中添加了换行符

理想情况下，您不想使用全局变量来存储状态。您将拥有另一个对象来存储状态或为您检索状态（可能从数据库）。在测试中，您将使用您的状态初始化此对象，然后检查您的函数是否将此状态作为输入正确执行。

以下是您下一步可以执行的简单示例。

main.go

//  todo struct (model)
type todo struct {
    id        string `json:"id"`
    task      string `json:"task"`
    completed bool   `json:"completed"`
}

type app struct {
    todos []todo
}

//  get all todos
func (a *app) gettodos(w http.responsewriter, r *http.request) {
    w.header().set("content-type", "application/json")
    json.newencoder(w).encode(a.todos)
}

func main() {
    // init router
    r := mux.newrouter()

    // mock data
    app := app{todos: []todo{
        {id: "1", task: "firsttask", completed: false},
        {id: "2", task: "secondtask", completed: false},
    }}

    fmt.println("go dude dude go ")

    r.handlefunc("/", func(w http.responsewriter, r *http.request) {
        fmt.fprint(w, "hello dudes")
    })

    r.handlefunc("/api/todos", app.gettodos).methods("get")

    log.fatal(http.listenandserve(":8080", r))
}

main_test.go

func TestGetTodos(t *testing.T) {
    req, err := http.NewRequest("GET", "/api/todos", nil)
    if err != nil {
        t.Fatal(err)
    }

    // Mock Data
    app := App{todos: []Todo{
        {Id: "1", Task: "FirstTask", Completed: false},
        {Id: "2", Task: "SecondTask", Completed: false},
    }}

    rr := httptest.NewRecorder()
    handler := http.HandlerFunc(app.GetTodos)
    handler.ServeHTTP(rr, req)
    if status := rr.Code; status != http.StatusOK {
        t.Errorf("handler returned wrong status code: got %v want %v",
            status, http.StatusOK)
    }

    // Check the response body is what we expect.
    expected := "[{\"id\":\"1\",\"task\":\"FirstTask\",\"completed\":false},{\"id\":\"2\",\"task\":\"SecondTask\",\"completed\":false}]\n"
    str := rr.Body.String()
    if diff := cmp.Diff(expected , str); diff != "" {
        t.Errorf("%s: mismatch (-want +got):\n%s", "", diff)
    }
    if str != expected {
        t.Errorf("handler returned unexpected body: got %v want %v",
            rr.Body.String(), expected)
    }
}

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