golang web开发 Handler测试利器httptest

test是golang语言的一部分，golang提供了非常强大的测试方法。单元测试，压力测试可以参见 golang 1.7之后高级测试方法之子测试，子基准测试(subtest sub-benchmarks)

我们用go开发一个Web Server后，打算单元测试写的handler函数，在不知道httptest之前，使用比较笨的方法
就是编译运行该Web Server后，再用go编写一个客户端程序向该Web Server对应的route发送数据然后解析
返回的数据。这个方法测试时非常麻烦，使用httptest来测试的话就非常简单，可以和testing测试一起使用。

httptest基本使用方法

假设在server中handler已经写好

http.HandleFunc("/health-check", HealthCheckHandler)func HealthCheckHandler(w http.ResponseWriter, r *http.Request) {    // A very simple health check.    w.WriteHeader(http.StatusOK)    w.Header().Set("Content-Type", "application/json")    // In the future we could report back on the status of our DB, or our cache     // (e.g. Redis) by performing a simple PING, and include them in the response.    io.WriteString(w, `{"alive": true}`)}

测试如下：

import (    "net/http"    "net/http/httptest"    "testing")func TestHealthCheckHandler(t *testing.T) {    //创建一个请求    req, err := http.NewRequest("GET", "/health-check", nil)    if err != nil {        t.Fatal(err)    }    // 我们创建一个 ResponseRecorder (which satisfies http.ResponseWriter)来记录响应    rr := httptest.NewRecorder()    //直接使用HealthCheckHandler，传入参数rr,req    HealthCheckHandler(rr, req)    // 检测返回的状态码    if status := rr.Code; status != http.StatusOK {        t.Errorf("handler returned wrong status code: got %v want %v",            status, http.StatusOK)    }    // 检测返回的数据    expected := `{"alive": true}`    if rr.Body.String() != expected {        t.Errorf("handler returned unexpected body: got %v want %v",            rr.Body.String(), expected)    }}

然后就可以使用run test来执行测试.

如果Web Server有操作数据库的行为，需要在init函数中进行数据库的连接。

参考官方文档中的样例编写的另外一个测试代码：

func TestHealthCheckHandler2(t *testing.T) {    reqData := struct {        Info string `json:"info"`    }{Info: "P123451"}    reqBody, _ := json.Marshal(reqData)    fmt.Println("input:", string(reqBody))    req := httptest.NewRequest(        http.MethodPost,        "/health-check",        bytes.NewReader(reqBody),    )    req.Header.Set("userid", "wdt")    req.Header.Set("commpay", "brk")    rr := httptest.NewRecorder()    HealthCheckHandler(rr, req)    result := rr.Result()    body, _ := ioutil.ReadAll(result.Body)    fmt.Println(string(body))    if result.StatusCode != http.StatusOK {        t.Errorf("expected status 200,",result.StatusCode)    }}

注意不同的地方
- http.NewRequest替换为httptest.NewRequest。
- httptest.NewRequest的第三个参数可以用来传递body数据，必须实现io.Reader接口。
- httptest.NewRequest不会返回error，无需进行err!=nil检查。
- 解析响应时没直接使用ResponseRecorder，而是调用了Result函数。

结合context使用

func TestGetProjectsHandler(t *testing.T) {    req, err := http.NewRequest("GET", "/api/users", nil)    if err != nil {        t.Fatal(err)    }    rr := httptest.NewRecorder()    // e.g. func GetUsersHandler(ctx context.Context, w http.ResponseWriter, r *http.Request)    handler := http.HandlerFunc(GetUsersHandler)    // Populate the request's context with our test data.    ctx := req.Context()    ctx = context.WithValue(ctx, "app.auth.token", "abc123")    ctx = context.WithValue(ctx, "app.user",        &YourUser{ID: "qejqjq", Email: "[e-mail]"})    // Add our context to the request: note that WithContext returns a copy of    // the request, which we must assign.    req = req.WithContext(ctx)    handler.ServeHTTP(rr, req)    // Check the status code is what we expect.    if status := rr.Code; status != http.StatusOK {        t.Errorf("handler returned wrong status code: got %v want %v",            status, http.StatusOK)    }}

参考

httptest doc
Testing Your (HTTP) Handlers in Go