logs: test JSON output with klog output test

The updated klog provides a reusable test suite for output handling.
Using it increases our test coverage without having to copy the test cases from
there into some JSON specific test suite.

test/integration/logs/functional/json/output_test.go

@@ -0,0 +1,78 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package json
+
+import (
+	"io"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/go-logr/logr"
+	"go.uber.org/zap/zapcore"
+
+	"k8s.io/component-base/config"
+	logsjson "k8s.io/component-base/logs/json"
+	"k8s.io/klog/v2/test"
+)
+
+func init() {
+	test.InitKlog()
+}
+
+// TestJsonOutput tests the JSON logger, directly and as backend for klog.
+func TestJSONOutput(t *testing.T) {
+	newLogger := func(out io.Writer, v int, vmodule string) logr.Logger {
+		logger, _ := logsjson.NewJSONLogger(config.VerbosityLevel(v), logsjson.AddNopSync(out), nil,
+			&zapcore.EncoderConfig{
+				MessageKey:     "msg",
+				CallerKey:      "caller",
+				NameKey:        "logger",
+				EncodeDuration: zapcore.StringDurationEncoder,
+				EncodeCaller:   zapcore.ShortCallerEncoder,
+			})
+		return logger
+	}
+
+	// If Go modules are turned off (for example, as in "make test-integration"),
+	// references to klog like k8s.io/klog/v2.ObjectRef.MarshalLog become
+	// k8s.io/kubernetes/vendor/k8s.io/klog/v2.ObjectRef.MarshalLog.
+	injectVendor := func(mapping map[string]string) map[string]string {
+		if os.Getenv("GO111MODULE") != "off" {
+			return mapping
+		}
+		for key, value := range mapping {
+			mapping[key] = strings.ReplaceAll(value, "k8s.io/klog/v2", "k8s.io/kubernetes/vendor/k8s.io/klog/v2")
+		}
+		return mapping
+	}
+
+	t.Run("direct", func(t *testing.T) {
+		test.Output(t, test.OutputConfig{
+			NewLogger:             newLogger,
+			ExpectedOutputMapping: injectVendor(test.ZaprOutputMappingDirect()),
+		})
+	})
+
+	t.Run("klog-backend", func(t *testing.T) {
+		test.Output(t, test.OutputConfig{
+			NewLogger:             newLogger,
+			AsBackend:             true,
+			ExpectedOutputMapping: injectVendor(test.ZaprOutputMappingIndirect()),
+		})
+	})
+}