kubelet: avoid manipulating global logger during unit test

The code as it stands now works, but it is still complicated and previous
versions had race
conditions (https://github.com/kubernetes/kubernetes/issues/108040). Now the
test works without modifying global state. The individual test cases could run
in parallel, this just isn't done because they complete quickly already (2
seconds).

pkg/kubelet/nodeshutdown/nodeshutdown_manager_linux_test.go

@@ -20,7 +20,6 @@ limitations under the License.
 package nodeshutdown
 
 import (
-	"bytes"
 	"fmt"
 	"os"
 	"strings"
@@ -35,7 +34,6 @@ import (
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/tools/record"
 	featuregatetesting "k8s.io/component-base/featuregate/testing"
-	"k8s.io/klog/v2"
 	"k8s.io/klog/v2/ktesting"
 	_ "k8s.io/klog/v2/ktesting/init" // activate ktesting command line flags
 	"k8s.io/kubernetes/pkg/apis/scheduling"
@@ -626,23 +624,6 @@ func Test_groupByPriority(t *testing.T) {
 	}
 }
 
-type buffer struct {
-	b  bytes.Buffer
-	rw sync.RWMutex
-}
-
-func (b *buffer) String() string {
-	b.rw.RLock()
-	defer b.rw.RUnlock()
-	return b.b.String()
-}
-
-func (b *buffer) Write(p []byte) (n int, err error) {
-	b.rw.Lock()
-	defer b.rw.Unlock()
-	return b.b.Write(p)
-}
-
 func Test_managerImpl_processShutdownEvent(t *testing.T) {
 	var (
 		probeManager   = probetest.FakeManager{}
@@ -669,7 +650,7 @@ func Test_managerImpl_processShutdownEvent(t *testing.T) {
 		name                   string
 		fields                 fields
 		wantErr                bool
-		exceptOutputContains string
+		expectedOutputContains string
 	}{
 		{
 			name: "kill pod func take too long",
@@ -702,20 +683,16 @@ func Test_managerImpl_processShutdownEvent(t *testing.T) {
 				dbusCon:        &fakeDbus{},
 			},
 			wantErr:                false,
-			exceptOutputContains: "Shutdown manager pod killing time out",
+			expectedOutputContains: "Shutdown manager pod killing time out",
 		},
 	}
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			l := klog.Level(1)
+			logger, _ := ktesting.NewTestContext(t)
-			l.Set("1")
-			// hijack the klog output
-			tmpWriteBuffer := new(buffer)
-			klog.SetOutput(tmpWriteBuffer)
-			klog.LogToStderr(false)
 
 			m := &managerImpl{
-				logger:                           klog.TODO(), // This test will be updated in a separate commit.
+				logger:                           logger,
 				recorder:                         tt.fields.recorder,
 				nodeRef:                          tt.fields.nodeRef,
 				probeManager:                     tt.fields.probeManager,
@@ -732,11 +709,17 @@ func Test_managerImpl_processShutdownEvent(t *testing.T) {
 			if err := m.processShutdownEvent(); (err != nil) != tt.wantErr {
 				t.Errorf("managerImpl.processShutdownEvent() error = %v, wantErr %v", err, tt.wantErr)
 			}
-			klog.Flush()
 
-			log := tmpWriteBuffer.String()
+			underlier, ok := logger.GetSink().(ktesting.Underlier)
-			if !strings.Contains(log, tt.exceptOutputContains) {
+			if !ok {
-				t.Errorf("managerImpl.processShutdownEvent() should log %s, got %s", tt.exceptOutputContains, log)
+				t.Fatalf("Should have had a ktesting LogSink, got %T", logger.GetSink())
+			}
+
+			log := underlier.GetBuffer().String()
+			if !strings.Contains(log, tt.expectedOutputContains) {
+				// Log will be shown on failure. To see it
+				// during a successful run use "go test -v".
+				t.Errorf("managerImpl.processShutdownEvent() should have logged %s, see actual output above.", tt.expectedOutputContains)
 			}
 		})
 	}