GolangAPI错误处理测试技巧

func FetchData(client *http.Client, url string) error {
    resp, err := client.Get(url)
    if err != nil {
        return fmt.Errorf("request failed: %w", err)
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        return fmt.Errorf("unexpected status: %d", resp.StatusCode)
    }
    return nil
}

func TestFetchData_ServerError(t *testing.T) {
    server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.WriteHeader(http.StatusInternalServerError)
    }))
    defer server.Close()

    client := &http.Client{}
    err := FetchData(client, server.URL)

    if err == nil {
        t.Fatal("expected error, got nil")
    }
    if !strings.Contains(err.Error(), "unexpected status: 500") {
        t.Errorf("wrong error message: %v", err)
    }
}

type failingRoundTripper struct{}

func (f *failingRoundTripper) RoundTrip(*http.Request) (*http.Response, error) {
    return nil, errors.New("connection refused")
}

func TestFetchData_NetworkFailure(t *testing.T) {
    client := &http.Client{
        Transport: &failingRoundTripper{},
    }

    err := FetchData(client, "https://example.com")

    if err == nil {
        t.Fatal("expected network error")
    }
    if !strings.Contains(err.Error(), "request failed") {
        t.Errorf("error should wrap network error")
    }
}

type HTTPError struct {
    StatusCode int
}

func (e *HTTPError) Error() string {
    return fmt.Sprintf("HTTP error: %d", e.StatusCode)
}

var httpErr *HTTPError
if errors.As(err, &httpErr) {
    if httpErr.StatusCode != 500 {
        t.Errorf("expected 500, got %d", httpErr.StatusCode)
    }
} else {
    t.Error("expected HTTPError")
}