[chore] fix flaky test for datadogreceiver server binding (#24895)

Use localhost:0 to get a free assignable port.

Fixes #24894

receiver/datadogreceiver/factory_test.go

@@ -15,6 +15,7 @@ import (
 func TestCreateReceiver(t *testing.T) {
 	factory := NewFactory()
 	cfg := factory.CreateDefaultConfig()
+	cfg.(*Config).Endpoint = "http://localhost:0"
 
 	tReceiver, err := factory.CreateTracesReceiver(context.Background(), receivertest.NewNopCreateSettings(), cfg, consumertest.NewNop())
 	assert.NoError(t, err)

receiver/datadogreceiver/receiver.go

@@ -17,6 +17,7 @@ import (
 )
 
 type datadogReceiver struct {
+	address      string
 	config       *Config
 	params       receiver.CreateSettings
 	nextConsumer consumer.Traces
@@ -66,6 +67,8 @@ func (ddr *datadogReceiver) Start(_ context.Context, host component.Host) error
 		return fmt.Errorf("failed to create datadog listener: %w", err)
 	}
 
+	ddr.address = hln.Addr().String()
+
 	go func() {
 		if err := ddr.server.Serve(hln); err != nil && !errors.Is(err, http.ErrServerClosed) {
 			host.ReportFatalError(fmt.Errorf("error starting datadog receiver: %w", err))

receiver/datadogreceiver/receiver_test.go

@@ -22,7 +22,9 @@ import (
 func TestDatadogReceiver_Lifecycle(t *testing.T) {
 
 	factory := NewFactory()
-	ddr, err := factory.CreateTracesReceiver(context.Background(), receivertest.NewNopCreateSettings(), factory.CreateDefaultConfig(), consumertest.NewNop())
+	cfg := factory.CreateDefaultConfig()
+	cfg.(*Config).Endpoint = "localhost:0"
+	ddr, err := factory.CreateTracesReceiver(context.Background(), receivertest.NewNopCreateSettings(), cfg, consumertest.NewNop())
 	assert.NoError(t, err, "Receiver should be created")
 
 	err = ddr.Start(context.Background(), componenttest.NewNopHost())
@@ -34,6 +36,7 @@ func TestDatadogReceiver_Lifecycle(t *testing.T) {
 
 func TestDatadogServer(t *testing.T) {
 	cfg := createDefaultConfig().(*Config)
+	cfg.Endpoint = "localhost:0" // Using a randomly assigned address
 	dd, err := newDataDogReceiver(
 		cfg,
 		consumertest.NewNop(),
@@ -69,7 +72,7 @@ func TestDatadogServer(t *testing.T) {
 
 			req, err := http.NewRequest(
 				http.MethodPost,
-				fmt.Sprintf("http://%s/v0.7/traces", cfg.Endpoint),
+				fmt.Sprintf("http://%s/v0.7/traces", dd.(*datadogReceiver).address),
 				tc.op,
 			)
 			require.NoError(t, err, "Must not error when creating request")