Add basic unit tests for the metrics package.

Author: creachadair

metrics/metrics_test.go

@@ -0,0 +1,95 @@
+package metrics_test
+
+import (
+	"testing"
+
+	"github.com/creachadair/jrpc2/metrics"
+)
+
+func getCount(m *metrics.M, name string) int64 {
+	c := make(map[string]int64)
+	m.Snapshot(metrics.Snapshot{Counter: c})
+	return c[name]
+}
+
+func getMax(m *metrics.M, name string) int64 {
+	mv := make(map[string]int64)
+	m.Snapshot(metrics.Snapshot{MaxValue: mv})
+	return mv[name]
+}
+
+func getLabel(m *metrics.M, name string) interface{} {
+	vs := make(map[string]interface{})
+	m.Snapshot(metrics.Snapshot{Label: vs})
+	return vs[name]
+}
+
+func TestMetrics(t *testing.T) {
+	m := metrics.New()
+	wantCount := func(name string, want int64) {
+		t.Helper()
+		got := getCount(m, name)
+		if got != want {
+			t.Errorf("Counter %q: got %d, want %d", name, got, want)
+		}
+	}
+	wantMax := func(name string, want int64) {
+		t.Helper()
+		got := getMax(m, name)
+		if got != want {
+			t.Errorf("MaxValue %q: got %d, want %d", name, got, want)
+		}
+	}
+	wantLabel := func(name string, want interface{}) {
+		t.Helper()
+		got := getLabel(m, name)
+		if got != want {
+			t.Errorf("Label %q: got %v, want %v", name, got, want)
+		}
+	}
+
+	wantCount("foo", 0)
+	m.Count("foo", 1)
+	wantCount("foo", 1)
+	m.Count("foo", 4)
+	wantCount("foo", 5)
+	m.Count("foo", -3)
+	wantCount("foo", 2)
+
+	wantMax("max", 0)
+	m.SetMaxValue("max", 10)
+	wantMax("max", 10)
+	m.SetMaxValue("max", 5)
+	wantMax("max", 10)
+	m.SetMaxValue("max", 12)
+	wantMax("max", 12)
+
+	m.CountAndSetMax("bar", 1)
+	wantCount("bar", 1)
+	wantMax("bar", 1)
+	m.CountAndSetMax("bar", 4)
+	wantCount("bar", 5)
+	wantMax("bar", 4)
+	m.CountAndSetMax("bar", -3)
+	wantCount("bar", 2)
+	wantMax("bar", 4)
+	m.CountAndSetMax("bar", 3)
+	wantCount("bar", 5)
+	wantMax("bar", 4)
+
+	wantLabel("hey", nil)
+	m.SetLabel("hey", "you")
+	wantLabel("hey", "you")
+	m.SetLabel("hey", nil)
+	wantLabel("hey", nil)
+
+	wantLabel("quux", nil)
+	m.EditLabel("quux", func(v interface{}) interface{} {
+		return "x"
+	})
+	wantLabel("quux", "x")
+	m.EditLabel("quux", func(v interface{}) interface{} {
+		return v.(string) + "2"
+	})
+	wantLabel("quux", "x2")
+}