有没有办法清除响应编写器中的数据？

Question

I am writing test for an elasticsearch middleware, where I am using a function to build test servers in which I pass a slice of configuration structs for each tests and in a handler function they are iterated upon and the expected response is written to the response writer. This is my function.

func newMockClient(url string) (*elasticsearch, error) {
    client, err := elastic.NewSimpleClient(elastic.SetURL(url))
    if err != nil {
        return nil, fmt.Errorf("error while initializing elastic client: %v", err)
    }
    es := &elasticsearch{
        url:    url,
        client: client,
    }
    return es, nil
}

type ServerSetup struct {
    Method, Path, Body, Response string
    HTTPStatus                   int
}

func buildTestServer(t *testing.T, setups []*ServerSetup) *httptest.Server {
    handlerFunc := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        requestBytes, _ := ioutil.ReadAll(r.Body)
        requestBody := string(requestBytes)

        matched := false
        for _, setup := range setups {
            if r.Method == setup.Method && r.URL.EscapedPath() == setup.Path {
                matched = true
                if setup.HTTPStatus == 0 {
                    w.WriteHeader(http.StatusOK)
                } else {
                    w.WriteHeader(setup.HTTPStatus)
                }
                _, err := w.Write([]byte(setup.Response))
                if err != nil {
                    t.Fatalf("Unable to write test server response: %v", err)
                }
            }
        }

        if !matched {
            t.Fatalf("No requests matched setup. Got method %s, Path %s, body %s", r.Method, r.URL.EscapedPath(), requestBody)
        }
    })

    return httptest.NewServer(handlerFunc)
}

It is copied from github.com/github/vulcanizer. When I run a single test using this, it works fine. For e.g. this test

func TestCreateIndex(t *testing.T) {
    setup := &ServerSetup{
        Method:   "PUT",
        Path:     "/test",
        Response: `{"acknowledged": true, "shards_acknowledged": true, "index": "test"}`,
    }

    ts := buildTestServer(t, []*ServerSetup{setup})

    es, _ := newMockClient(ts.URL)

    err := es.createIndex(context.Background(), "test", nil)
    if err != nil {
        t.Fatalf("Index creation failed with error: %v
", err)
    }

}

But when I try to check different behaviours in a single test like this one I get an error http: multiple response.WriteHeader calls

func TestDeleteIndex(t *testing.T) {
    setup := &ServerSetup{
        Method:   "DELETE",
        Path:     "/test",
        Response: `{"acknowledged": true}`,
    }

    errSetup := &ServerSetup{
        Method:   "DELETE",
        Path:     "/test",
        Response: `{"acknowledged": false}`,
    }

    ctx := context.Background()

    ts := buildTestServer(t, []*ServerSetup{setup, errSetup})
    defer ts.Close()

    es, _ := newMockClient(ts.URL)

    err := es.deleteIndex(ctx, "test")
    if err != nil {
        t.Fatalf("Index creation failed with error: %v
", err)
    }

    err = es.deleteIndex(ctx, "test")
    if err == nil {
        t.Fatal("Expected error but not found")
    }
}

I am guessing that it is because of the fact that when I run deleteIndex for the second time it pings the server again but the response writer has already been written to so it can't write anything else to it.

Is there anyway I can have a check at the beginning of my handler func like

handlerFunc := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    if w != nil{
        // clear data in response writer
    }

// .........



}

Answer 1

I don't think what you are doing is the correct way to test your functionality. You need to separate your test to test-cases for checking different behaviours like that:

func Test_DeleteIndex(t *testing.T) {
    t.Run("Should be ok with correct setup", func(t *testing.T) {
        setup := &ServerSetup{
            Method:   "DELETE",
            Path:     "/test",
            Response: `{"acknowledged": true}`,
        }
        ctx := context.Background()
        ts := buildTestServer(t, []*ServerSetup{setup})
        defer ts.Close()
        es, _ := newMockClient(ts.URL)
        err := es.deleteIndex(ctx, "test")
        require.NoError(t, err)
    })

    t.Run("Shouldn't be ok with wrong setup", func(t *testing.T) {
        setup := &ServerSetup{
            Method:   "DELETE",
            Path:     "/test",
            Response: `{"acknowledged": false}`,
        }
        ctx := context.Background()
        ts := buildTestServer(t, []*ServerSetup{setup})
        defer ts.Close()
        es, _ := newMockClient(ts.URL)
        err := es.deleteIndex(ctx, "test")
        require.Error(t, err)
    })
}