test(network): re-add Test_conn_startSending with deterministic ordering (#4432)

The test was removed on master in #2618 because it was flaky: it
cancelled the stream before calling disconnect(), racing the receive
goroutine (which stores the stream error as close status) against
disconnect() cancelling the connection context. Disconnecting first
guarantees the context is cancelled before RecvMsg returns, making the
test deterministic while restoring the goroutine-exit and no-panic
coverage. Verified with -race -count=100.

Assisted-by: AI

Author: stevenvegt

network/transport/grpc/connection_test.go

@@ -20,8 +20,11 @@ package grpc
 
 import (
 	"context"
+	"github.com/nuts-foundation/nuts-node/test"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -101,6 +104,33 @@ func Test_conn_registerStream(t *testing.T) {
 	})
 }
 
+func Test_conn_startSending(t *testing.T) {
+	t.Run("disconnect does not panic", func(t *testing.T) {
+		connection := createConnection(context.Background(), transport.Peer{}).(*conn)
+		stream := newServerStream("foo", "", nil)
+
+		defer stream.cancelFunc()
+
+		p := &TestProtocol{}
+		_ = connection.registerStream(p, stream)
+
+		assert.Equal(t, int32(2), connection.activeGoroutines) // startSending and startReceiving
+
+		// Disconnect before cancelling the stream: this guarantees the connection context is
+		// cancelled before RecvMsg returns, so the receive loop drops the message instead of
+		// racing to store the stream error as close status.
+		connection.disconnect()
+		stream.cancelFunc()
+
+		test.WaitFor(t, func() (bool, error) {
+			return atomic.LoadInt32(&connection.activeGoroutines) == 0, nil
+		}, 5*time.Second, "waiting for all goroutines to exit")
+
+		// A deliberate local disconnect must not record a close error. Default value is OK.
+		assert.Equal(t, codes.OK, connection.status.Load().Code())
+	})
+}
+
 func TestConn_Send(t *testing.T) {
 	t.Run("buffer overflow softlimit", func(t *testing.T) {
 		connection := createConnection(context.Background(), transport.Peer{}).(*conn)