GO·NOTE

一份 Go 开发工程师的学习笔记

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测试代码如何写的更好？

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1、结果输出在代码下面

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func ExampleHasPrefix() {
	fmt.Println(bytes.HasPrefix([]byte("Gopher"), []byte("Go")))
	fmt.Println(bytes.HasPrefix([]byte("Gopher"), []byte("C")))
	fmt.Println(bytes.HasPrefix([]byte("Gopher"), []byte("")))
	// Output:
	// true
	// false
	// true
}

2、方法、参数、错误都打印出来

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func TestNonpollableDeadline(t *testing.T) {
	// On BSD systems regular files seem to be pollable,
	// so just run this test on Linux.
	if runtime.GOOS != "linux" {
		t.Skipf("skipping on %s", runtime.GOOS)
	}

	f, err := ioutil.TempFile("", "ostest")
	if err != nil {
		t.Fatal(err)
	}
	defer os.Remove(f.Name())
	defer f.Close()
	deadline := time.Now().Add(10 * time.Second)
	if err := f.SetDeadline(deadline); err != os.ErrNoDeadline {
		t.Errorf("SetDeadline on file returned %v, wanted %v", err, os.ErrNoDeadline)
	}
	if err := f.SetReadDeadline(deadline); err != os.ErrNoDeadline {
		t.Errorf("SetReadDeadline on file returned %v, wanted %v", err, os.ErrNoDeadline)
	}
	if err := f.SetWriteDeadline(deadline); err != os.ErrNoDeadline {
		t.Errorf("SetWriteDeadline on file returned %v, wanted %v", err, os.ErrNoDeadline)
	}
}

WaitGroup() 的wait 可以直接用defer实现

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// TestRacyRead tests that it is safe to mutate the input Read buffer
// immediately after cancellation has occurred.
func TestRacyRead(t *testing.T) {
	t.Parallel()

	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	defer r.Close()
	defer w.Close()

	var wg sync.WaitGroup
	defer wg.Wait()

	go io.Copy(w, rand.New(rand.NewSource(0)))

	r.SetReadDeadline(time.Now().Add(time.Millisecond))
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()

			b1 := make([]byte, 1024)
			b2 := make([]byte, 1024)
			for j := 0; j < 100; j++ {
				_, err := r.Read(b1)
				copy(b1, b2) // Mutate b1 to trigger potential race
				if err != nil {
					if !os.IsTimeout(err) {
						t.Error(err)
					}
					r.SetReadDeadline(time.Now().Add(time.Millisecond))
				}
			}
		}()
	}
}