client: add a simple test for counter

client_test.go

@@ -266,6 +266,8 @@ func matchMetricsAndValues(metrics map[uint64]*mmvdump.Metric, values map[uint64
 			matchSingletonMetricAndValue(met, metrics, values, t)
 		case *PCPInstanceMetric:
 			matchInstanceMetricAndValues(met, metrics, values, t)
+		case *PCPCounter:
+			matchSingletonMetricAndValue(met.PCPSingletonMetric, metrics, values, t)
 		}
 	}
 }
@@ -713,3 +715,28 @@ func TestWritingDifferentTypes(t *testing.T) {
 	matchMetricsAndValues(metrics, values, c, t)
 	matchInstancesAndInstanceDomains(instances, indoms, c, t)
 }
+
+func TestCounter(t *testing.T) {
+	c, err := NewPCPClient("test", ProcessFlag)
+	if err != nil {
+		t.Errorf("cannot create client, error: %v", err)
+	}
+
+	m, err := NewPCPCounter(0, "c.1")
+	if err != nil {
+		t.Errorf("cannot create counter, error: %v", err)
+	}
+
+	c.MustRegister(m)
+
+	c.MustStart()
+	defer c.MustStop()
+
+	_, _, metrics, values, _, _, _, err := mmvdump.Dump(c.buffer.Bytes())
+	if err != nil {
+		t.Errorf("cannot get dump: %v", err)
+		return
+	}
+
+	matchMetricsAndValues(metrics, values, c, t)
+}