n := 2
	running := make(chan bool, n)
	awake := make(chan bool, n)
	for i := 0; i < n; i++ {
		go func() {
			m.Lock()
			running <- true
			c.Wait()
			awake <- true
			m.Unlock()
		}()
	}
	for i := 0; i < n; i++ {
		<-running // Wait for everyone to run.
	}
	for n > 0 {
		select {
		case <-awake:
			t.Fatal("goroutine not asleep")
		default:
		}
		m.Lock()
		c.Signal()
		m.Unlock()

			sum += i
		}
		fmt.Println("Computed once:", sum)
		return sum
	})
	done := make(chan bool)
	for i := 0; i < 10; i++ {
		go func() {
			const want = 499500
			got := once()
			if got != want {
				fmt.Println("want", want, "got", got)
			}
			done <- true
		}()
	}
	for i := 0; i < 10; i++ {
		<-done
	}
	// Output:
	// Computed once: 499500
}

				k, v := next[int](), next[int32]()
				m[k] = v
				c.Put(k, v)
			}
			barrier.Done()
			barrier.Wait()

			for k, v := range m {
				if cv := c.Get(k); cv != v {
					t.Errorf("c.Get(%v) = %v, want %v", str(k), str(cv), str(v))
					atomic.AddInt32(&lost, +1)
				}
			}
		}()
	}
	wg.Wait()
	if lost != 0 {
		t.Errorf("lost %d entries", lost)
	}

		if len(events) == 0 {
			return
		}
		select {
		case e := <-fx.Events:
			found := false
			for i, want := range events {
				if e.Type == want.Type &&
					(want.ID == "" || e.ID == want.ID) &&
					(want.Namespace == "" || want.Namespace == e.Namespace) &&
					(want.EndpointCount == 0 || want.EndpointCount == len(e.Endpoints)) {
					// Matched - delete event from desired
					events = slices.Delete(events, i)

	}
	transformer := &envelopeTransformer{}

	want := sets.NewInt()
	startCh := make(chan struct{})
	wg := sync.WaitGroup{}
	for i := 0; i < 100; i++ {
		want.Insert(i + 1)
		k := fmt.Sprintf("key-%d", i)
		wg.Add(1)
		go func(key string) {
			defer wg.Done()
			<-startCh
			cache.set([]byte(key), transformer)
		}(k)
	}
	close(startCh)
	wg.Wait()

	got := sets.NewInt()

	f(t, c1, c2)
}

// testBasicIO tests that the data sent on c1 is properly received on c2.
func testBasicIO(t *testing.T, c1, c2 net.Conn) {
	want := make([]byte, 1<<20)
	rand.New(rand.NewSource(0)).Read(want)

	dataCh := make(chan []byte)
	go func() {
		rd := bytes.NewReader(want)
		if err := chunkedCopy(c1, rd); err != nil {
			t.Errorf("unexpected c1.Write error: %v", err)
		}
		if err := c1.Close(); err != nil {

		// This error was surfaced from a background process by a call to Wait.
		// Add a call frame for Wait itself, but ignore its "want" field.
		// (Wait itself cannot fail to wait on commands or else it would leak
		// processes and/or goroutines — so a negative assertion for it would be at
		// best ambiguous.)
		return cmdError(cmd, err)
	}

	if cmd.want == success {
		return cmdError(cmd, err)
	}

	c, err := Dial("tcp", ln.Addr().String())
	if err != nil {
		t.Fatal(err)
	}
	defer c.Close()

	buf := new(bytes.Buffer)
	buf.ReadFrom(c)

	if want, have := "Produced ", buf.String(); have != want {
		t.Errorf("unexpected server reply %q, want %q", have, want)
	}

	for err := range errc {
		t.Error(err)
	}
}

func TestSendfileSeeked(t *testing.T) {
	ln := newLocalListener(t, "tcp")

	c, stop := NotifyContext(parent, syscall.SIGINT)
	defer stop()

	if want, got := "signal.NotifyContext(context.Background.WithCancel, [interrupt])", fmt.Sprint(c); want != got {
		t.Errorf("c.String() = %q, want %q", got, want)
	}

	cancelParent()
	<-c.Done()
	if got := c.Err(); got != context.Canceled {
		t.Errorf("c.Err() = %q, want %q", got, context.Canceled)
	}
}

	tests := []struct {
		name string
		err  error
		want bool
	}{
		{
			err:  ErrWaitTimeout,
			want: true,
		},
		{
			err:  context.Canceled,
			want: true,
		}, {
			err:  context.DeadlineExceeded,
			want: true,
		},
		{
			err:  errWrapper{ErrWaitTimeout},
			want: true,
		},
		{
			err:  errWrapper{context.Canceled},
			want: true,
		},
		{