redis: refactor change signal test to be more deterministic (#2335)

pkg/storage/redis/redis_test.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sync/errgroup"
 	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/types/known/anypb"
 	"google.golang.org/protobuf/types/known/timestamppb"
@@ -129,39 +130,53 @@ func TestChangeSignal(t *testing.T) {
 	defer cancel()
 
 	require.NoError(t, testutil.WithTestRedis(false, func(rawURL string) error {
-		backend1, err := New(rawURL)
-		require.NoError(t, err)
-		defer func() { _ = backend1.Close() }()
-
-		backend2, err := New(rawURL)
-		require.NoError(t, err)
-		defer func() { _ = backend2.Close() }()
-
-		ch := backend1.onChange.Bind()
-		defer backend1.onChange.Unbind(ch)
-
-		go func() {
-			ticker := time.NewTicker(time.Millisecond * 100)
-			defer ticker.Stop()
-			for {
-				_, _ = backend2.Put(ctx, &databroker.Record{
-					Type: "TYPE",
-					Id:   "ID",
-				})
-				select {
-				case <-ctx.Done():
-					return
-				case <-ticker.C:
-				}
+		ready := make(chan struct{})
+		var eg errgroup.Group
+		eg.Go(func() error {
+			backend, err := New(rawURL)
+			if err != nil {
+				return err
 			}
-		}()
+			defer func() { _ = backend.Close() }()
 
-		select {
-		case <-ch:
-		case <-ctx.Done():
-			t.Fatal("expected signal to be fired when another backend triggers a change")
-		}
+			ch := backend.onChange.Bind()
+			defer backend.onChange.Unbind(ch)
 
+			// signal the second backend that we're ready to receive a change
+			close(ready)
+
+			select {
+			case <-ch:
+			case <-ctx.Done():
+				return ctx.Err()
+			}
+			return nil
+		})
+		eg.Go(func() error {
+			// wait for the first backend to be bound to the on change handler
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-ready:
+			}
+
+			backend, err := New(rawURL)
+			if err != nil {
+				return err
+			}
+			defer func() { _ = backend.Close() }()
+
+			// put a new value to trigger a change
+			_, err = backend.Put(ctx, &databroker.Record{
+				Type: "TYPE",
+				Id:   "ID",
+			})
+			if err != nil {
+				return err
+			}
+			return nil
+		})
+		assert.NoError(t, eg.Wait(), "expected signal to be fired when another backend triggers a change")
 		return nil
 	}))
 }