Add a testlogger util package for testing go-logr.

Signed-off-by: Matt Moyer <moyerm@vmware.com>

go.mod

@@ -5,6 +5,8 @@ go 1.14
 require (
 	github.com/davecgh/go-spew v1.1.1
 	github.com/go-logr/logr v0.2.1
+	github.com/go-logr/stdr v0.2.0
+	github.com/go-logr/zapr v0.2.0 // indirect
 	github.com/golang/mock v1.4.4
 	github.com/golangci/golangci-lint v1.31.0
 	github.com/google/go-cmp v0.5.2

go.sum

@@ -149,6 +149,10 @@ github.com/go-logr/logr v0.2.0 h1:QvGt2nLcHH0WK9orKa+ppBPAxREcH364nPUedEpK0TY=
 github.com/go-logr/logr v0.2.0/go.mod h1:z6/tIYblkpsD+a4lm/fGIIU9mZ+XfAiaFtq7xTgseGU=
 github.com/go-logr/logr v0.2.1 h1:fV3MLmabKIZ383XifUjFSwcoGee0v9qgPp8wy5svibE=
 github.com/go-logr/logr v0.2.1/go.mod h1:z6/tIYblkpsD+a4lm/fGIIU9mZ+XfAiaFtq7xTgseGU=
+github.com/go-logr/stdr v0.2.0 h1:EuTFw3BCZ6H/+1VNFlOLVK/sPKwmGMLx8/FTOFWuXpU=
+github.com/go-logr/stdr v0.2.0/go.mod h1:NO1vneyJDqKVgJYnxhwXWWmQPOvNM391IG3H8ql3jiA=
+github.com/go-logr/zapr v0.2.0 h1:v6Ji8yBW77pva6NkJKQdHLAJKrIJKRHz0RXwPqCHSR4=
+github.com/go-logr/zapr v0.2.0/go.mod h1:qhKdvif7YF5GI9NWEpyxTSSBdGmzkNguibrdCNVPunU=
 github.com/go-ole/go-ole v1.2.1/go.mod h1:7FAglXiTm7HKlQRDeOQ6ZNUHidzCWXuZWq/1dTyBNF8=
 github.com/go-openapi/jsonpointer v0.0.0-20160704185906-46af16f9f7b1/go.mod h1:+35s3my2LFTysnkMfxsJBAMHj/DoqoB9knIWoYG/Vk0=
 github.com/go-openapi/jsonpointer v0.19.2/go.mod h1:3akKfEdA7DF1sugOqz1dVQHBcuDBPKZGEoHC/NkiQRg=
@@ -622,6 +626,7 @@ go.uber.org/atomic v1.4.0 h1:cxzIVoETapQEqDhQu3QfnvXAV4AlzcvUCxkVUFw3+EU=
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
+go.uber.org/zap v1.8.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
 go.uber.org/zap v1.10.0 h1:ORx85nbTijNz8ljznvCMR1ZBIPKFn3jQrag10X2AsuM=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=

internal/testutil/testlogger/testlogger.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+// Package testlogger implements a logr.Logger suitable for writing test assertions.
+package testlogger
+
+import (
+	"bytes"
+	"log"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/go-logr/logr"
+	"github.com/go-logr/stdr"
+)
+
+// Logger implements logr.Logger in a way that captures logs for test assertions.
+type Logger struct {
+	logr.Logger
+	t      *testing.T
+	buffer syncBuffer
+}
+
+// New returns a new test Logger.
+func New(t *testing.T) *Logger {
+	res := Logger{t: t}
+	res.Logger = stdr.New(log.New(&res.buffer, "", 0))
+	return &res
+}
+
+// Lines returns the lines written to the test logger.
+func (l *Logger) Lines() []string {
+	l.t.Helper()
+	l.buffer.mutex.Lock()
+	defer l.buffer.mutex.Unlock()
+
+	// Trim leading/trailing whitespace and omit empty lines.
+	var result []string
+	for _, line := range strings.Split(l.buffer.buffer.String(), "\n") {
+		line = strings.TrimSpace(line)
+		if line != "" {
+			result = append(result, line)
+		}
+	}
+	return result
+}
+
+// syncBuffer synchronizes access to a bytes.Buffer.
+type syncBuffer struct {
+	mutex  sync.Mutex
+	buffer bytes.Buffer
+}
+
+func (s *syncBuffer) Write(p []byte) (n int, err error) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.buffer.Write(p)
+}