test: fix TestNewReceiver race conditions (#42084) (#42090)

update zapcore to use observer zaptest package to avoid
race condition on zapLogs bytes.Buffer

use atomic for countLogs to avoid race condition on
primitive type

(cherry picked from commit d115014)

Co-authored-by: kruskall <[email protected]>

x-pack/metricbeat/mbreceiver/receiver_test.go

@@ -5,8 +5,8 @@
 package mbreceiver
 
 import (
-	"bytes"
 	"context"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -16,6 +16,7 @@ import (
 	"go.opentelemetry.io/collector/receiver"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
+	"go.uber.org/zap/zaptest/observer"
 )
 
 func TestNewReceiver(t *testing.T) {
@@ -45,24 +46,20 @@ func TestNewReceiver(t *testing.T) {
 		},
 	}
 
-	var zapLogs bytes.Buffer
-	core := zapcore.NewCore(
-		zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig()),
-		zapcore.AddSync(&zapLogs),
-		zapcore.DebugLevel)
+	core, logs := observer.New(zapcore.DebugLevel)
 
 	receiverSettings := receiver.Settings{}
 	receiverSettings.Logger = zap.New(core)
 
-	var countLogs int
+	var countLogs atomic.Int64
 	logConsumer, err := consumer.NewLogs(func(ctx context.Context, ld plog.Logs) error {
-		countLogs = countLogs + ld.LogRecordCount()
+		countLogs.Add(int64(ld.LogRecordCount()))
 		return nil
 	})
 	require.NoError(t, err, "Error creating log consumer")
 
 	r, err := createReceiver(context.Background(), receiverSettings, &config, logConsumer)
-	require.NoErrorf(t, err, "Error creating receiver. Logs:\n %s", zapLogs.String())
+	require.NoErrorf(t, err, "Error creating receiver. Logs:\n %s", logs.All())
 	err = r.Start(context.Background(), nil)
 	require.NoError(t, err, "Error starting metricbeatreceiver")
 
@@ -75,10 +72,10 @@ func TestNewReceiver(t *testing.T) {
 	for tick := ticker.C; ; {
 		select {
 		case <-timer.C:
-			t.Fatalf("consumed logs didn't increase\nCount: %d\nLogs: %s\n", countLogs, zapLogs.String())
+			t.Fatalf("consumed logs didn't increase\nCount: %d\nLogs: %v\n", countLogs.Load(), logs.All())
 		case <-tick:
 			tick = nil
-			go func() { ch <- countLogs > 0 }()
+			go func() { ch <- countLogs.Load() > 0 }()
 		case v := <-ch:
 			if v {
 				goto found