make exporter more testable

exporter/googlecloudpubsubexporter/exporter.go

@@ -33,6 +33,10 @@ type pubsubExporter struct {
 	metricsWatermarkFunc metricsWatermarkFunc
 	logsMarshaler        plog.Marshaler
 	logsWatermarkFunc    logsWatermarkFunc
+
+	// To be overridden in tests
+	makeUUID   func() (uuid.UUID, error)
+	makeClient func(ctx context.Context, cfg *Config, userAgent string) (publisherClient, error)
 }
 
 type encoding int
@@ -61,7 +65,7 @@ func (ex *pubsubExporter) start(ctx context.Context, _ component.Host) error {
 	ctx, ex.cancel = context.WithCancel(ctx)
 
 	if ex.client == nil {
-		client, err := newPublisherClient(ctx, ex.config, ex.userAgent)
+		client, err := ex.makeClient(ctx, ex.config, ex.userAgent)
 		if err != nil {
 			return fmt.Errorf("failed creating the gRPC client to Pubsub: %w", err)
 		}
@@ -82,7 +86,7 @@ func (ex *pubsubExporter) shutdown(_ context.Context) error {
 }
 
 func (ex *pubsubExporter) publishMessage(ctx context.Context, encoding encoding, data []byte, watermark time.Time) error {
-	id, err := uuid.NewRandom()
+	id, err := ex.makeUUID()
 	if err != nil {
 		return err
 	}

exporter/googlecloudpubsubexporter/factory.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/google/uuid"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/exporter"
@@ -51,6 +52,8 @@ func ensureExporter(params exporter.Settings, pCfg *Config) *pubsubExporter {
 		tracesMarshaler:  &ptrace.ProtoMarshaler{},
 		metricsMarshaler: &pmetric.ProtoMarshaler{},
 		logsMarshaler:    &plog.ProtoMarshaler{},
+		makeUUID:         uuid.NewRandom,
+		makeClient:       newPublisherClient,
 	}
 	// we ignore the error here as the config is already validated with the same method
 	receiver.ceCompression, _ = pCfg.parseCompression()