test: add test case

utils/metric/counter_test.go

@@ -0,0 +1,23 @@
+package metric
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCounter(t *testing.T) {
+	assert := assert.New(t)
+	c := NewCounter()
+	c.Inc(10)
+	assert.EqualValues(10, c.Count())
+
+	c.Dec(5)
+	assert.EqualValues(5, c.Count())
+
+	cTmp := c.Snapshot()
+	assert.EqualValues(5, cTmp.Count())
+
+	c.Clear()
+	assert.EqualValues(0, c.Count())
+}