client: add support and fix tests

client.go

@@ -477,6 +477,11 @@ func (c *PCPClient) writeMetrics() {
 				c.writeInstanceMetric(metric)
 				wg.Done()
 			}(metric)
+		case *PCPCounter:
+			go func(metric *PCPCounter) {
+				c.writeSingletonMetric(metric.PCPSingletonMetric)
+				wg.Done()
+			}(metric)
 		}
 	}
 

client_test.go

@@ -845,7 +845,7 @@ func TestMMV2InstanceWriting(t *testing.T) {
 }
 
 func TestCounter(t *testing.T) {
-	c, err := NewPCPClient("test", ProcessFlag)
+	c, err := NewPCPClient("test")
 	if err != nil {
 		t.Errorf("cannot create client, error: %v", err)
 	}
@@ -860,12 +860,47 @@ func TestCounter(t *testing.T) {
 	c.MustStart()
 	defer c.MustStop()
 
-	_, _, metrics, values, _, _, _, err := mmvdump.Dump(c.buffer.Bytes())
+	_, _, metrics, values, _, _, strings, err := mmvdump.Dump(c.writer.Bytes())
 	if err != nil {
 		t.Errorf("cannot get dump: %v", err)
 		return
 	}
 
-	matchMetricsAndValues(metrics, values, c, t)
-}
+	matchMetricsAndValues(metrics, values, strings, c, t)
+
+	m.Up()
+
+	_, _, metrics, values, _, _, _, err = mmvdump.Dump(c.writer.Bytes())
+
+	off, _ := findMetric(m, metrics)
+	_, v := findValue(off, values)
+
+	if val, _ := mmvdump.FixedVal(v.Val, mmvdump.Int64Type); val != int64(1) {
+		t.Errorf("expected counter to be 1 after Up(), got %v", val)
+	}
+
+	m.MustInc(9)
+
+	_, _, metrics, values, _, _, _, err = mmvdump.Dump(c.writer.Bytes())
 
+	off, _ = findMetric(m, metrics)
+	_, v = findValue(off, values)
+
+	if val, _ := mmvdump.FixedVal(v.Val, mmvdump.Int64Type); val != int64(10) {
+		t.Errorf("expected counter to be 10 after Set(10), got %v", val)
+	}
+
+	err = m.Inc(-9)
+	if err == nil {
+		t.Errorf("expected decrementing a counter to generate an error")
+	}
+
+	_, _, metrics, values, _, _, _, err = mmvdump.Dump(c.writer.Bytes())
+
+	off, _ = findMetric(m, metrics)
+	_, v = findValue(off, values)
+
+	if val, _ := mmvdump.FixedVal(v.Val, mmvdump.Int64Type); val != int64(10) {
+		t.Errorf("expected counter to stay at 10 after Set(-9), got %v", val)
+	}
+}