integration: rewrite the way to check cluster make progress

integration/cluster_test.go

@@ -57,15 +57,7 @@ func testCluster(t *testing.T, size int) {
 	c := NewCluster(t, size)
 	c.Launch(t)
 	defer c.Terminate(t)
-	for i, u := range c.URLs() {
-		cc := mustNewHTTPClient(t, []string{u})
-		kapi := client.NewKeysAPI(cc)
-		ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
-		if _, err := kapi.Create(ctx, fmt.Sprintf("/%d", i), "bar", -1); err != nil {
-			t.Errorf("create on %s error: %v", u, err)
-		}
-		cancel()
-	}
+	clusterMustProgress(t, c)
 }
 
 func TestClusterOf1UsingDiscovery(t *testing.T) { testClusterUsingDiscovery(t, 1) }
@@ -88,13 +80,28 @@ func testClusterUsingDiscovery(t *testing.T, size int) {
 	c := NewClusterByDiscovery(t, size, dc.URL(0)+"/v2/keys")
 	c.Launch(t)
 	defer c.Terminate(t)
+	clusterMustProgress(t, c)
+}
+
+// clusterMustProgress ensures that cluster can make progress. It creates
+// a key first, and check the new key could be got from all client urls of
+// the cluster.
+func clusterMustProgress(t *testing.T, cl *cluster) {
+	cc := mustNewHTTPClient(t, []string{cl.URL(0)})
+	kapi := client.NewKeysAPI(cc)
+	ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
+	resp, err := kapi.Create(ctx, "/foo", "bar", -1)
+	if err != nil {
+		t.Fatalf("create on %s error: %v", cl.URL(0), err)
+	}
+	cancel()
 
-	for i, u := range c.URLs() {
+	for i, u := range cl.URLs() {
 		cc := mustNewHTTPClient(t, []string{u})
 		kapi := client.NewKeysAPI(cc)
 		ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
-		if _, err := kapi.Create(ctx, fmt.Sprintf("/%d", i), "bar", -1); err != nil {
-			t.Errorf("create on %s error: %v", u, err)
+		if _, err := kapi.Watch("foo", resp.Node.ModifiedIndex).Next(ctx); err != nil {
+			t.Fatalf("#%d: watch on %s error: %v", i, u, err)
 		}
 		cancel()
 	}