if e != nil {
		return e
	}
	defer f.Close()
	_, e = f.Write([]byte(data))
	return e
}

func (p *Process) signal(sig Signal) error {
	switch p.pidStatus() {
	case statusDone:
		return ErrProcessDone
	case statusReleased:
		return syscall.ENOENT
	}

	if e := p.writeProcFile("note", sig.String()); e != nil {
		return NewSyscallError("signal", e)
	}

	// completes its wait.
	//
	// Checking for statusDone here would not be a complete fix, as the PID
	// could still be waited on and reused prior to blockUntilWaitable.
	switch p.pidStatus() {
	case statusReleased:
		return nil, syscall.EINVAL
	}

	// If we can block until Wait4 will succeed immediately, do so.
	ready, err := p.blockUntilWaitable()
	if err != nil {
		return nil, err
	}

// and the blocking GetNewerThan() method. The component responsible for
// populating the cache is expected to call Delete() to explicitly free the
// cache entries.
type Cache interface {
	Get(types.UID) (*PodStatus, error)
	// Set updates the cache by setting the PodStatus for the pod only
	// if the data is newer than the cache based on the provided
	// time stamp. Returns if the cache was updated.

	for desc, test := range map[string]struct {
		pod               *v1.Pod
		status            *kubecontainer.PodStatus
		expectedChanged   bool
		expectedAttempt   uint32
		expectedSandboxID string
	}{
		"Pod with no existing sandboxes": {
			pod:               &v1.Pod{},
			status:            &kubecontainer.PodStatus{},
			expectedChanged:   true,
			expectedAttempt:   0,
			expectedSandboxID: "",
		},

func matchOnExitCodes(podStatus *v1.PodStatus, requirement *batch.PodFailurePolicyOnExitCodesRequirement) *v1.ContainerStatus {
	if containerStatus := getMatchingContainerFromList(podStatus.ContainerStatuses, requirement); containerStatus != nil {
		return containerStatus
	}
	return getMatchingContainerFromList(podStatus.InitContainerStatuses, requirement)
}

			podMap: map[types.UID][]*v1.Pod{
				"uid-1": {
					{
						Status: v1.PodStatus{
							Phase: v1.PodFailed,
						},
					},
					{
						Status: v1.PodStatus{
							Phase: v1.PodSucceeded,
						},
					},
				},
				"uid-2": {},
				"uid-3": {
					{
						Status: v1.PodStatus{
							Phase: v1.PodPending,
						},
					},
				},
			},

// (changed, new attempt, original sandboxID if exist).
func PodSandboxChanged(pod *v1.Pod, podStatus *kubecontainer.PodStatus) (bool, uint32, string) {
	if len(podStatus.SandboxStatuses) == 0 {
		klog.V(2).InfoS("No sandbox for pod can be found. Need to start a new one", "pod", klog.KObj(pod))
		return true, 0, ""
	}

	readySandboxCount := 0
	for _, s := range podStatus.SandboxStatuses {
		if s.State == runtimeapi.PodSandboxState_SANDBOX_READY {

	podManager.SetPods(pods)
	// The original test here is totally meaningless, because fakeruntime will always return an empty podStatus. While
	// the original logic of isPodRunning happens to return true when podstatus is empty, so the test can always pass.
	// Now the logic in isPodRunning is changed, to let the test pass, we set the podstatus directly in fake runtime.

		})
	}

	SimplePods.Register(TrackerHandler[SimplePod](tt))

	pod := &corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{
			Name:      "name",
			Namespace: "namespace",
		},
		Status: corev1.PodStatus{PodIP: "1.2.3.4"},
	}
	pc.CreateOrUpdateStatus(pod)
	tt.WaitUnordered("add/namespace/name")
	assert.Equal(t, fetchSorted("1.2.3.4"), []SimplePod{{NewNamed(pod), Labeled{}, "1.2.3.4"}})

	pod.Status.PodIP = "1.2.3.5"

	pod := &corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{
			Name:      "test",
			Namespace: "test",
		},
		Spec: corev1.PodSpec{
			NodeName: "derp",
		},
		Status: corev1.PodStatus{
			PodIP: "11.1.1.12",
		},
	}

	podIPs := GetPodIPsIfPresent(pod)
	assert.Equal(t, len(podIPs), 1)
}

func TestGetPodIPsIfPodIPPresent(t *testing.T) {
	pod := &corev1.Pod{