Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 956 insertions, 0 deletions

diff --git a/src/context/x_test.go b/src/context/x_test.go
new file mode 100644
index 0000000..57fe60b
--- /dev/null
+++ b/src/context/x_test.go
@@ -0,0 +1,956 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package context_test
+
+import (
+	. "context"
+	"errors"
+	"fmt"
+	"math/rand"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// Each XTestFoo in context_test.go must be called from a TestFoo here to run.
+func TestParentFinishesChild(t *testing.T) {
+	XTestParentFinishesChild(t) // uses unexported context types
+}
+func TestChildFinishesFirst(t *testing.T) {
+	XTestChildFinishesFirst(t) // uses unexported context types
+}
+func TestCancelRemoves(t *testing.T) {
+	XTestCancelRemoves(t) // uses unexported context types
+}
+func TestCustomContextGoroutines(t *testing.T) {
+	XTestCustomContextGoroutines(t) // reads the context.goroutines counter
+}
+
+// The following are regular tests in package context_test.
+
+// otherContext is a Context that's not one of the types defined in context.go.
+// This lets us test code paths that differ based on the underlying type of the
+// Context.
+type otherContext struct {
+	Context
+}
+
+const (
+	shortDuration    = 1 * time.Millisecond // a reasonable duration to block in a test
+	veryLongDuration = 1000 * time.Hour     // an arbitrary upper bound on the test's running time
+)
+
+// quiescent returns an arbitrary duration by which the program should have
+// completed any remaining work and reached a steady (idle) state.
+func quiescent(t *testing.T) time.Duration {
+	deadline, ok := t.Deadline()
+	if !ok {
+		return 5 * time.Second
+	}
+
+	const arbitraryCleanupMargin = 1 * time.Second
+	return time.Until(deadline) - arbitraryCleanupMargin
+}
+func TestBackground(t *testing.T) {
+	c := Background()
+	if c == nil {
+		t.Fatalf("Background returned nil")
+	}
+	select {
+	case x := <-c.Done():
+		t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+	default:
+	}
+	if got, want := fmt.Sprint(c), "context.Background"; got != want {
+		t.Errorf("Background().String() = %q want %q", got, want)
+	}
+}
+
+func TestTODO(t *testing.T) {
+	c := TODO()
+	if c == nil {
+		t.Fatalf("TODO returned nil")
+	}
+	select {
+	case x := <-c.Done():
+		t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+	default:
+	}
+	if got, want := fmt.Sprint(c), "context.TODO"; got != want {
+		t.Errorf("TODO().String() = %q want %q", got, want)
+	}
+}
+
+func TestWithCancel(t *testing.T) {
+	c1, cancel := WithCancel(Background())
+
+	if got, want := fmt.Sprint(c1), "context.Background.WithCancel"; got != want {
+		t.Errorf("c1.String() = %q want %q", got, want)
+	}
+
+	o := otherContext{c1}
+	c2, _ := WithCancel(o)
+	contexts := []Context{c1, o, c2}
+
+	for i, c := range contexts {
+		if d := c.Done(); d == nil {
+			t.Errorf("c[%d].Done() == %v want non-nil", i, d)
+		}
+		if e := c.Err(); e != nil {
+			t.Errorf("c[%d].Err() == %v want nil", i, e)
+		}
+
+		select {
+		case x := <-c.Done():
+			t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+		default:
+		}
+	}
+
+	cancel() // Should propagate synchronously.
+	for i, c := range contexts {
+		select {
+		case <-c.Done():
+		default:
+			t.Errorf("<-c[%d].Done() blocked, but shouldn't have", i)
+		}
+		if e := c.Err(); e != Canceled {
+			t.Errorf("c[%d].Err() == %v want %v", i, e, Canceled)
+		}
+	}
+}
+
+func testDeadline(c Context, name string, t *testing.T) {
+	t.Helper()
+	d := quiescent(t)
+	timer := time.NewTimer(d)
+	defer timer.Stop()
+	select {
+	case <-timer.C:
+		t.Fatalf("%s: context not timed out after %v", name, d)
+	case <-c.Done():
+	}
+	if e := c.Err(); e != DeadlineExceeded {
+		t.Errorf("%s: c.Err() == %v; want %v", name, e, DeadlineExceeded)
+	}
+}
+
+func TestDeadline(t *testing.T) {
+	t.Parallel()
+
+	c, _ := WithDeadline(Background(), time.Now().Add(shortDuration))
+	if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+		t.Errorf("c.String() = %q want prefix %q", got, prefix)
+	}
+	testDeadline(c, "WithDeadline", t)
+
+	c, _ = WithDeadline(Background(), time.Now().Add(shortDuration))
+	o := otherContext{c}
+	testDeadline(o, "WithDeadline+otherContext", t)
+
+	c, _ = WithDeadline(Background(), time.Now().Add(shortDuration))
+	o = otherContext{c}
+	c, _ = WithDeadline(o, time.Now().Add(veryLongDuration))
+	testDeadline(c, "WithDeadline+otherContext+WithDeadline", t)
+
+	c, _ = WithDeadline(Background(), time.Now().Add(-shortDuration))
+	testDeadline(c, "WithDeadline+inthepast", t)
+
+	c, _ = WithDeadline(Background(), time.Now())
+	testDeadline(c, "WithDeadline+now", t)
+}
+
+func TestTimeout(t *testing.T) {
+	t.Parallel()
+
+	c, _ := WithTimeout(Background(), shortDuration)
+	if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+		t.Errorf("c.String() = %q want prefix %q", got, prefix)
+	}
+	testDeadline(c, "WithTimeout", t)
+
+	c, _ = WithTimeout(Background(), shortDuration)
+	o := otherContext{c}
+	testDeadline(o, "WithTimeout+otherContext", t)
+
+	c, _ = WithTimeout(Background(), shortDuration)
+	o = otherContext{c}
+	c, _ = WithTimeout(o, veryLongDuration)
+	testDeadline(c, "WithTimeout+otherContext+WithTimeout", t)
+}
+
+func TestCanceledTimeout(t *testing.T) {
+	c, _ := WithTimeout(Background(), time.Second)
+	o := otherContext{c}
+	c, cancel := WithTimeout(o, veryLongDuration)
+	cancel() // Should propagate synchronously.
+	select {
+	case <-c.Done():
+	default:
+		t.Errorf("<-c.Done() blocked, but shouldn't have")
+	}
+	if e := c.Err(); e != Canceled {
+		t.Errorf("c.Err() == %v want %v", e, Canceled)
+	}
+}
+
+type key1 int
+type key2 int
+
+var k1 = key1(1)
+var k2 = key2(1) // same int as k1, different type
+var k3 = key2(3) // same type as k2, different int
+
+func TestValues(t *testing.T) {
+	check := func(c Context, nm, v1, v2, v3 string) {
+		if v, ok := c.Value(k1).(string); ok == (len(v1) == 0) || v != v1 {
+			t.Errorf(`%s.Value(k1).(string) = %q, %t want %q, %t`, nm, v, ok, v1, len(v1) != 0)
+		}
+		if v, ok := c.Value(k2).(string); ok == (len(v2) == 0) || v != v2 {
+			t.Errorf(`%s.Value(k2).(string) = %q, %t want %q, %t`, nm, v, ok, v2, len(v2) != 0)
+		}
+		if v, ok := c.Value(k3).(string); ok == (len(v3) == 0) || v != v3 {
+			t.Errorf(`%s.Value(k3).(string) = %q, %t want %q, %t`, nm, v, ok, v3, len(v3) != 0)
+		}
+	}
+
+	c0 := Background()
+	check(c0, "c0", "", "", "")
+
+	c1 := WithValue(Background(), k1, "c1k1")
+	check(c1, "c1", "c1k1", "", "")
+
+	if got, want := fmt.Sprint(c1), `context.Background.WithValue(type context_test.key1, val c1k1)`; got != want {
+		t.Errorf("c.String() = %q want %q", got, want)
+	}
+
+	c2 := WithValue(c1, k2, "c2k2")
+	check(c2, "c2", "c1k1", "c2k2", "")
+
+	c3 := WithValue(c2, k3, "c3k3")
+	check(c3, "c2", "c1k1", "c2k2", "c3k3")
+
+	c4 := WithValue(c3, k1, nil)
+	check(c4, "c4", "", "c2k2", "c3k3")
+
+	o0 := otherContext{Background()}
+	check(o0, "o0", "", "", "")
+
+	o1 := otherContext{WithValue(Background(), k1, "c1k1")}
+	check(o1, "o1", "c1k1", "", "")
+
+	o2 := WithValue(o1, k2, "o2k2")
+	check(o2, "o2", "c1k1", "o2k2", "")
+
+	o3 := otherContext{c4}
+	check(o3, "o3", "", "c2k2", "c3k3")
+
+	o4 := WithValue(o3, k3, nil)
+	check(o4, "o4", "", "c2k2", "")
+}
+
+func TestAllocs(t *testing.T) {
+	bg := Background()
+	for _, test := range []struct {
+		desc       string
+		f          func()
+		limit      float64
+		gccgoLimit float64
+	}{
+		{
+			desc:       "Background()",
+			f:          func() { Background() },
+			limit:      0,
+			gccgoLimit: 0,
+		},
+		{
+			desc: fmt.Sprintf("WithValue(bg, %v, nil)", k1),
+			f: func() {
+				c := WithValue(bg, k1, nil)
+				c.Value(k1)
+			},
+			limit:      3,
+			gccgoLimit: 3,
+		},
+		{
+			desc: "WithTimeout(bg, 1*time.Nanosecond)",
+			f: func() {
+				c, _ := WithTimeout(bg, 1*time.Nanosecond)
+				<-c.Done()
+			},
+			limit:      12,
+			gccgoLimit: 15,
+		},
+		{
+			desc: "WithCancel(bg)",
+			f: func() {
+				c, cancel := WithCancel(bg)
+				cancel()
+				<-c.Done()
+			},
+			limit:      5,
+			gccgoLimit: 8,
+		},
+		{
+			desc: "WithTimeout(bg, 5*time.Millisecond)",
+			f: func() {
+				c, cancel := WithTimeout(bg, 5*time.Millisecond)
+				cancel()
+				<-c.Done()
+			},
+			limit:      8,
+			gccgoLimit: 25,
+		},
+	} {
+		limit := test.limit
+		if runtime.Compiler == "gccgo" {
+			// gccgo does not yet do escape analysis.
+			// TODO(iant): Remove this when gccgo does do escape analysis.
+			limit = test.gccgoLimit
+		}
+		numRuns := 100
+		if testing.Short() {
+			numRuns = 10
+		}
+		if n := testing.AllocsPerRun(numRuns, test.f); n > limit {
+			t.Errorf("%s allocs = %f want %d", test.desc, n, int(limit))
+		}
+	}
+}
+
+func TestSimultaneousCancels(t *testing.T) {
+	root, cancel := WithCancel(Background())
+	m := map[Context]CancelFunc{root: cancel}
+	q := []Context{root}
+	// Create a tree of contexts.
+	for len(q) != 0 && len(m) < 100 {
+		parent := q[0]
+		q = q[1:]
+		for i := 0; i < 4; i++ {
+			ctx, cancel := WithCancel(parent)
+			m[ctx] = cancel
+			q = append(q, ctx)
+		}
+	}
+	// Start all the cancels in a random order.
+	var wg sync.WaitGroup
+	wg.Add(len(m))
+	for _, cancel := range m {
+		go func(cancel CancelFunc) {
+			cancel()
+			wg.Done()
+		}(cancel)
+	}
+
+	d := quiescent(t)
+	stuck := make(chan struct{})
+	timer := time.AfterFunc(d, func() { close(stuck) })
+	defer timer.Stop()
+
+	// Wait on all the contexts in a random order.
+	for ctx := range m {
+		select {
+		case <-ctx.Done():
+		case <-stuck:
+			buf := make([]byte, 10<<10)
+			n := runtime.Stack(buf, true)
+			t.Fatalf("timed out after %v waiting for <-ctx.Done(); stacks:\n%s", d, buf[:n])
+		}
+	}
+	// Wait for all the cancel functions to return.
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-stuck:
+		buf := make([]byte, 10<<10)
+		n := runtime.Stack(buf, true)
+		t.Fatalf("timed out after %v waiting for cancel functions; stacks:\n%s", d, buf[:n])
+	}
+}
+
+func TestInterlockedCancels(t *testing.T) {
+	parent, cancelParent := WithCancel(Background())
+	child, cancelChild := WithCancel(parent)
+	go func() {
+		<-parent.Done()
+		cancelChild()
+	}()
+	cancelParent()
+	d := quiescent(t)
+	timer := time.NewTimer(d)
+	defer timer.Stop()
+	select {
+	case <-child.Done():
+	case <-timer.C:
+		buf := make([]byte, 10<<10)
+		n := runtime.Stack(buf, true)
+		t.Fatalf("timed out after %v waiting for child.Done(); stacks:\n%s", d, buf[:n])
+	}
+}
+
+func TestLayersCancel(t *testing.T) {
+	testLayers(t, time.Now().UnixNano(), false)
+}
+
+func TestLayersTimeout(t *testing.T) {
+	testLayers(t, time.Now().UnixNano(), true)
+}
+
+func testLayers(t *testing.T, seed int64, testTimeout bool) {
+	t.Parallel()
+
+	r := rand.New(rand.NewSource(seed))
+	errorf := func(format string, a ...any) {
+		t.Errorf(fmt.Sprintf("seed=%d: %s", seed, format), a...)
+	}
+	const (
+		minLayers = 30
+	)
+	type value int
+	var (
+		vals      []*value
+		cancels   []CancelFunc
+		numTimers int
+		ctx       = Background()
+	)
+	for i := 0; i < minLayers || numTimers == 0 || len(cancels) == 0 || len(vals) == 0; i++ {
+		switch r.Intn(3) {
+		case 0:
+			v := new(value)
+			ctx = WithValue(ctx, v, v)
+			vals = append(vals, v)
+		case 1:
+			var cancel CancelFunc
+			ctx, cancel = WithCancel(ctx)
+			cancels = append(cancels, cancel)
+		case 2:
+			var cancel CancelFunc
+			d := veryLongDuration
+			if testTimeout {
+				d = shortDuration
+			}
+			ctx, cancel = WithTimeout(ctx, d)
+			cancels = append(cancels, cancel)
+			numTimers++
+		}
+	}
+	checkValues := func(when string) {
+		for _, key := range vals {
+			if val := ctx.Value(key).(*value); key != val {
+				errorf("%s: ctx.Value(%p) = %p want %p", when, key, val, key)
+			}
+		}
+	}
+	if !testTimeout {
+		select {
+		case <-ctx.Done():
+			errorf("ctx should not be canceled yet")
+		default:
+		}
+	}
+	if s, prefix := fmt.Sprint(ctx), "context.Background."; !strings.HasPrefix(s, prefix) {
+		t.Errorf("ctx.String() = %q want prefix %q", s, prefix)
+	}
+	t.Log(ctx)
+	checkValues("before cancel")
+	if testTimeout {
+		d := quiescent(t)
+		timer := time.NewTimer(d)
+		defer timer.Stop()
+		select {
+		case <-ctx.Done():
+		case <-timer.C:
+			errorf("ctx should have timed out after %v", d)
+		}
+		checkValues("after timeout")
+	} else {
+		cancel := cancels[r.Intn(len(cancels))]
+		cancel()
+		select {
+		case <-ctx.Done():
+		default:
+			errorf("ctx should be canceled")
+		}
+		checkValues("after cancel")
+	}
+}
+
+func TestWithCancelCanceledParent(t *testing.T) {
+	parent, pcancel := WithCancelCause(Background())
+	cause := fmt.Errorf("Because!")
+	pcancel(cause)
+
+	c, _ := WithCancel(parent)
+	select {
+	case <-c.Done():
+	default:
+		t.Errorf("child not done immediately upon construction")
+	}
+	if got, want := c.Err(), Canceled; got != want {
+		t.Errorf("child not canceled; got = %v, want = %v", got, want)
+	}
+	if got, want := Cause(c), cause; got != want {
+		t.Errorf("child has wrong cause; got = %v, want = %v", got, want)
+	}
+}
+
+func TestWithCancelSimultaneouslyCanceledParent(t *testing.T) {
+	// Cancel the parent goroutine concurrently with creating a child.
+	for i := 0; i < 100; i++ {
+		parent, pcancel := WithCancelCause(Background())
+		cause := fmt.Errorf("Because!")
+		go pcancel(cause)
+
+		c, _ := WithCancel(parent)
+		<-c.Done()
+		if got, want := c.Err(), Canceled; got != want {
+			t.Errorf("child not canceled; got = %v, want = %v", got, want)
+		}
+		if got, want := Cause(c), cause; got != want {
+			t.Errorf("child has wrong cause; got = %v, want = %v", got, want)
+		}
+	}
+}
+
+func TestWithValueChecksKey(t *testing.T) {
+	panicVal := recoveredValue(func() { _ = WithValue(Background(), []byte("foo"), "bar") })
+	if panicVal == nil {
+		t.Error("expected panic")
+	}
+	panicVal = recoveredValue(func() { _ = WithValue(Background(), nil, "bar") })
+	if got, want := fmt.Sprint(panicVal), "nil key"; got != want {
+		t.Errorf("panic = %q; want %q", got, want)
+	}
+}
+
+func TestInvalidDerivedFail(t *testing.T) {
+	panicVal := recoveredValue(func() { _, _ = WithCancel(nil) })
+	if panicVal == nil {
+		t.Error("expected panic")
+	}
+	panicVal = recoveredValue(func() { _, _ = WithDeadline(nil, time.Now().Add(shortDuration)) })
+	if panicVal == nil {
+		t.Error("expected panic")
+	}
+	panicVal = recoveredValue(func() { _ = WithValue(nil, "foo", "bar") })
+	if panicVal == nil {
+		t.Error("expected panic")
+	}
+}
+
+func recoveredValue(fn func()) (v any) {
+	defer func() { v = recover() }()
+	fn()
+	return
+}
+
+func TestDeadlineExceededSupportsTimeout(t *testing.T) {
+	i, ok := DeadlineExceeded.(interface {
+		Timeout() bool
+	})
+	if !ok {
+		t.Fatal("DeadlineExceeded does not support Timeout interface")
+	}
+	if !i.Timeout() {
+		t.Fatal("wrong value for timeout")
+	}
+}
+func TestCause(t *testing.T) {
+	var (
+		forever       = 1e6 * time.Second
+		parentCause   = fmt.Errorf("parentCause")
+		childCause    = fmt.Errorf("childCause")
+		tooSlow       = fmt.Errorf("tooSlow")
+		finishedEarly = fmt.Errorf("finishedEarly")
+	)
+	for _, test := range []struct {
+		name  string
+		ctx   func() Context
+		err   error
+		cause error
+	}{
+		{
+			name:  "Background",
+			ctx:   Background,
+			err:   nil,
+			cause: nil,
+		},
+		{
+			name:  "TODO",
+			ctx:   TODO,
+			err:   nil,
+			cause: nil,
+		},
+		{
+			name: "WithCancel",
+			ctx: func() Context {
+				ctx, cancel := WithCancel(Background())
+				cancel()
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithCancelCause",
+			ctx: func() Context {
+				ctx, cancel := WithCancelCause(Background())
+				cancel(parentCause)
+				return ctx
+			},
+			err:   Canceled,
+			cause: parentCause,
+		},
+		{
+			name: "WithCancelCause nil",
+			ctx: func() Context {
+				ctx, cancel := WithCancelCause(Background())
+				cancel(nil)
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithCancelCause: parent cause before child",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancelCause(Background())
+				ctx, cancelChild := WithCancelCause(ctx)
+				cancelParent(parentCause)
+				cancelChild(childCause)
+				return ctx
+			},
+			err:   Canceled,
+			cause: parentCause,
+		},
+		{
+			name: "WithCancelCause: parent cause after child",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancelCause(Background())
+				ctx, cancelChild := WithCancelCause(ctx)
+				cancelChild(childCause)
+				cancelParent(parentCause)
+				return ctx
+			},
+			err:   Canceled,
+			cause: childCause,
+		},
+		{
+			name: "WithCancelCause: parent cause before nil",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancelCause(Background())
+				ctx, cancelChild := WithCancel(ctx)
+				cancelParent(parentCause)
+				cancelChild()
+				return ctx
+			},
+			err:   Canceled,
+			cause: parentCause,
+		},
+		{
+			name: "WithCancelCause: parent cause after nil",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancelCause(Background())
+				ctx, cancelChild := WithCancel(ctx)
+				cancelChild()
+				cancelParent(parentCause)
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithCancelCause: child cause after nil",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancel(Background())
+				ctx, cancelChild := WithCancelCause(ctx)
+				cancelParent()
+				cancelChild(childCause)
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithCancelCause: child cause before nil",
+			ctx: func() Context {
+				ctx, cancelParent := WithCancel(Background())
+				ctx, cancelChild := WithCancelCause(ctx)
+				cancelChild(childCause)
+				cancelParent()
+				return ctx
+			},
+			err:   Canceled,
+			cause: childCause,
+		},
+		{
+			name: "WithTimeout",
+			ctx: func() Context {
+				ctx, cancel := WithTimeout(Background(), 0)
+				cancel()
+				return ctx
+			},
+			err:   DeadlineExceeded,
+			cause: DeadlineExceeded,
+		},
+		{
+			name: "WithTimeout canceled",
+			ctx: func() Context {
+				ctx, cancel := WithTimeout(Background(), forever)
+				cancel()
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithTimeoutCause",
+			ctx: func() Context {
+				ctx, cancel := WithTimeoutCause(Background(), 0, tooSlow)
+				cancel()
+				return ctx
+			},
+			err:   DeadlineExceeded,
+			cause: tooSlow,
+		},
+		{
+			name: "WithTimeoutCause canceled",
+			ctx: func() Context {
+				ctx, cancel := WithTimeoutCause(Background(), forever, tooSlow)
+				cancel()
+				return ctx
+			},
+			err:   Canceled,
+			cause: Canceled,
+		},
+		{
+			name: "WithTimeoutCause stacked",
+			ctx: func() Context {
+				ctx, cancel := WithCancelCause(Background())
+				ctx, _ = WithTimeoutCause(ctx, 0, tooSlow)
+				cancel(finishedEarly)
+				return ctx
+			},
+			err:   DeadlineExceeded,
+			cause: tooSlow,
+		},
+		{
+			name: "WithTimeoutCause stacked canceled",
+			ctx: func() Context {
+				ctx, cancel := WithCancelCause(Background())
+				ctx, _ = WithTimeoutCause(ctx, forever, tooSlow)
+				cancel(finishedEarly)
+				return ctx
+			},
+			err:   Canceled,
+			cause: finishedEarly,
+		},
+		{
+			name: "WithoutCancel",
+			ctx: func() Context {
+				return WithoutCancel(Background())
+			},
+			err:   nil,
+			cause: nil,
+		},
+		{
+			name: "WithoutCancel canceled",
+			ctx: func() Context {
+				ctx, cancel := WithCancelCause(Background())
+				ctx = WithoutCancel(ctx)
+				cancel(finishedEarly)
+				return ctx
+			},
+			err:   nil,
+			cause: nil,
+		},
+		{
+			name: "WithoutCancel timeout",
+			ctx: func() Context {
+				ctx, cancel := WithTimeoutCause(Background(), 0, tooSlow)
+				ctx = WithoutCancel(ctx)
+				cancel()
+				return ctx
+			},
+			err:   nil,
+			cause: nil,
+		},
+	} {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			ctx := test.ctx()
+			if got, want := ctx.Err(), test.err; want != got {
+				t.Errorf("ctx.Err() = %v want %v", got, want)
+			}
+			if got, want := Cause(ctx), test.cause; want != got {
+				t.Errorf("Cause(ctx) = %v want %v", got, want)
+			}
+		})
+	}
+}
+
+func TestCauseRace(t *testing.T) {
+	cause := errors.New("TestCauseRace")
+	ctx, cancel := WithCancelCause(Background())
+	go func() {
+		cancel(cause)
+	}()
+	for {
+		// Poll Cause, rather than waiting for Done, to test that
+		// access to the underlying cause is synchronized properly.
+		if err := Cause(ctx); err != nil {
+			if err != cause {
+				t.Errorf("Cause returned %v, want %v", err, cause)
+			}
+			break
+		}
+		runtime.Gosched()
+	}
+}
+
+func TestWithoutCancel(t *testing.T) {
+	key, value := "key", "value"
+	ctx := WithValue(Background(), key, value)
+	ctx = WithoutCancel(ctx)
+	if d, ok := ctx.Deadline(); !d.IsZero() || ok != false {
+		t.Errorf("ctx.Deadline() = %v, %v want zero, false", d, ok)
+	}
+	if done := ctx.Done(); done != nil {
+		t.Errorf("ctx.Deadline() = %v want nil", done)
+	}
+	if err := ctx.Err(); err != nil {
+		t.Errorf("ctx.Err() = %v want nil", err)
+	}
+	if v := ctx.Value(key); v != value {
+		t.Errorf("ctx.Value(%q) = %q want %q", key, v, value)
+	}
+}
+
+type customDoneContext struct {
+	Context
+	donec chan struct{}
+}
+
+func (c *customDoneContext) Done() <-chan struct{} {
+	return c.donec
+}
+
+func TestCustomContextPropagation(t *testing.T) {
+	cause := errors.New("TestCustomContextPropagation")
+	donec := make(chan struct{})
+	ctx1, cancel1 := WithCancelCause(Background())
+	ctx2 := &customDoneContext{
+		Context: ctx1,
+		donec:   donec,
+	}
+	ctx3, cancel3 := WithCancel(ctx2)
+	defer cancel3()
+
+	cancel1(cause)
+	close(donec)
+
+	<-ctx3.Done()
+	if got, want := ctx3.Err(), Canceled; got != want {
+		t.Errorf("child not canceled; got = %v, want = %v", got, want)
+	}
+	if got, want := Cause(ctx3), cause; got != want {
+		t.Errorf("child has wrong cause; got = %v, want = %v", got, want)
+	}
+}
+
+func TestAfterFuncCalledAfterCancel(t *testing.T) {
+	ctx, cancel := WithCancel(Background())
+	donec := make(chan struct{})
+	stop := AfterFunc(ctx, func() {
+		close(donec)
+	})
+	select {
+	case <-donec:
+		t.Fatalf("AfterFunc called before context is done")
+	case <-time.After(shortDuration):
+	}
+	cancel()
+	select {
+	case <-donec:
+	case <-time.After(veryLongDuration):
+		t.Fatalf("AfterFunc not called after context is canceled")
+	}
+	if stop() {
+		t.Fatalf("stop() = true, want false")
+	}
+}
+
+func TestAfterFuncCalledAfterTimeout(t *testing.T) {
+	ctx, cancel := WithTimeout(Background(), shortDuration)
+	defer cancel()
+	donec := make(chan struct{})
+	AfterFunc(ctx, func() {
+		close(donec)
+	})
+	select {
+	case <-donec:
+	case <-time.After(veryLongDuration):
+		t.Fatalf("AfterFunc not called after context is canceled")
+	}
+}
+
+func TestAfterFuncCalledImmediately(t *testing.T) {
+	ctx, cancel := WithCancel(Background())
+	cancel()
+	donec := make(chan struct{})
+	AfterFunc(ctx, func() {
+		close(donec)
+	})
+	select {
+	case <-donec:
+	case <-time.After(veryLongDuration):
+		t.Fatalf("AfterFunc not called for already-canceled context")
+	}
+}
+
+func TestAfterFuncNotCalledAfterStop(t *testing.T) {
+	ctx, cancel := WithCancel(Background())
+	donec := make(chan struct{})
+	stop := AfterFunc(ctx, func() {
+		close(donec)
+	})
+	if !stop() {
+		t.Fatalf("stop() = false, want true")
+	}
+	cancel()
+	select {
+	case <-donec:
+		t.Fatalf("AfterFunc called for already-canceled context")
+	case <-time.After(shortDuration):
+	}
+	if stop() {
+		t.Fatalf("stop() = true, want false")
+	}
+}
+
+// This test verifies that cancelling a context does not block waiting for AfterFuncs to finish.
+func TestAfterFuncCalledAsynchronously(t *testing.T) {
+	ctx, cancel := WithCancel(Background())
+	donec := make(chan struct{})
+	stop := AfterFunc(ctx, func() {
+		// The channel send blocks until donec is read from.
+		donec <- struct{}{}
+	})
+	defer stop()
+	cancel()
+	// After cancel returns, read from donec and unblock the AfterFunc.
+	select {
+	case <-donec:
+	case <-time.After(veryLongDuration):
+		t.Fatalf("AfterFunc not called after context is canceled")
+	}
+}