test: Add unit test for channel state waiting for first resolver update

test/clientconn_state_transition_test.go

@@ -36,6 +36,7 @@ import (
 	"google.golang.org/grpc/internal/balancer/stub"
 	"google.golang.org/grpc/internal/envconfig"
 	"google.golang.org/grpc/internal/grpcsync"
+	"google.golang.org/grpc/internal/stubserver"
 	"google.golang.org/grpc/internal/testutils"
 	"google.golang.org/grpc/resolver"
 	"google.golang.org/grpc/resolver/manual"
@@ -616,3 +617,40 @@ func (s) TestConnectivityStateSubscriber(t *testing.T) {
 		}
 	}
 }
+
+// TestChannelStateWaitingForFirstResolverUpdate verifies the initial
+// state of the channel when a manual name resolver doesn't provide any updates.
+func (s) TestChannelStateWaitingForFirstResolverUpdate(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test.")
+	}
+
+	backend := stubserver.StartTestService(t, nil)
+	defer backend.Stop()
+
+	mr := manual.NewBuilderWithScheme("e2e-test")
+	defer mr.Close()
+
+	cc, err := grpc.NewClient(mr.Scheme()+":///", grpc.WithResolvers(mr), grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Fatalf("Failed to create new client: %v", err)
+	}
+	defer cc.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	testutils.AwaitState(ctx, t, cc, connectivity.Idle)
+
+	cc.Connect()
+
+	time.Sleep(100 * time.Millisecond)
+
+	testutils.AwaitState(ctx, t, cc, connectivity.Connecting)
+
+	mr.UpdateState(resolver.State{
+		Addresses: []resolver.Address{{Addr: backend.Address}},
+	})
+
+	testutils.AwaitState(ctx, t, cc, connectivity.Ready)
+}