Tests cribbed from Coda.

.gitignore

@@ -1,5 +1,7 @@
 *.[68]
 *.a
+*.out
 *.swp
 _obj
 cmd/metrics/metrics
+_testmain.go

counter_test.go

@@ -0,0 +1,53 @@
+package metrics
+
+import (
+	"testing"
+)
+
+func TestCounterZero(t *testing.T) {
+	c := NewCounter()
+	if count := c.Count(); 0 != count {
+		t.Errorf("c.Count(): 0 != %v\n", count)
+	}
+}
+
+func TestCounterInc1(t *testing.T) {
+	c := NewCounter()
+	c.Inc(1)
+	if count := c.Count(); 1 != count {
+		t.Errorf("c.Count(): 1 != %v\n", count)
+	}
+}
+
+func TestCounterInc12(t *testing.T) {
+	c := NewCounter()
+	c.Inc(12)
+	if count := c.Count(); 12 != count {
+		t.Errorf("c.Count(): 12 != %v\n", count)
+	}
+}
+
+func TestCounterDec1(t *testing.T) {
+	c := NewCounter()
+	c.Dec(1)
+	if count := c.Count(); -1 != count {
+		t.Errorf("c.Count(): -1 != %v\n", count)
+	}
+}
+
+func TestCounterDec12(t *testing.T) {
+	c := NewCounter()
+	c.Dec(12)
+	if count := c.Count(); -12 != count {
+		t.Errorf("c.Count(): -12 != %v\n", count)
+	}
+}
+
+func TestCounterClear(t *testing.T) {
+	c := NewCounter()
+	c.Inc(3)
+	c.Clear()
+	if count := c.Count(); 0 != count {
+		t.Errorf("c.Count(): 0 != %v\n", count)
+	}
+}

gauge_test.go

@@ -0,0 +1,13 @@
+package metrics
+
+import (
+	"testing"
+)
+
+func TestGauge(t *testing.T) {
+	g := NewGauge()
+	g.Update(int64(47))
+	if v := g.Value(); 47 != v {
+		t.Errorf("g.Value(): 47 != %v\n", v)
+	}
+}

histogram_test.go

@@ -0,0 +1,64 @@
+package metrics
+
+import (
+	"testing"
+)
+
+func TestEmptyHistogram(t *testing.T) {
+	h := NewHistogram(NewUniformSample(100))
+	if count := h.Count(); 0 != count {
+		t.Errorf("h.Count(): 0 != %v\n", count)
+	}
+	if min := h.Min(); 0 != min {
+		t.Errorf("h.Min(): 0 != %v\n", min)
+	}
+	if max := h.Max(); 0 != max {
+		t.Errorf("h.Max(): 0 != %v\n", max)
+	}
+	if mean := h.Mean(); 0.0 != mean {
+		t.Errorf("h.Mean(): 0.0 != %v\n", mean)
+	}
+	if stdDev := h.StdDev(); 0.0 != stdDev {
+		t.Errorf("h.StdDev(): 0.0 != %v\n", stdDev)
+	}
+	ps := h.Percentiles([]float64{0.5, 0.75, 0.99})
+	if 0.0 != ps[0] {
+		t.Errorf("median: 0.0 != %v\n", ps[0])
+	}
+	if 0.0 != ps[1] {
+		t.Errorf("75th percentile: 0.0 != %v\n", ps[1])
+	}
+	if 0.0 != ps[2] {
+		t.Errorf("99th percentile: 0.0 != %v\n", ps[2])
+	}
+}
+
+func TestHistogram10000(t *testing.T) {
+	h := NewHistogram(NewUniformSample(100000))
+	for i := 1; i <= 10000; i++ { h.Update(int64(i)) }
+	if count := h.Count(); 10000 != count {
+		t.Errorf("h.Count(): 10000 != %v\n", count)
+	}
+	if min := h.Min(); 1 != min {
+		t.Errorf("h.Min(): 1 != %v\n", min)
+	}
+	if max := h.Max(); 10000 != max {
+		t.Errorf("h.Max(): 10000 != %v\n", max)
+	}
+	if mean := h.Mean(); 5000.5 != mean {
+		t.Errorf("h.Mean(): 5000.5 != %v\n", mean)
+	}
+	if stdDev := h.StdDev(); 2886.8956799071675 != stdDev {
+		t.Errorf("h.StdDev(): 2886.8956799071675 != %v\n", stdDev)
+	}
+	ps := h.Percentiles([]float64{0.5, 0.75, 0.99})
+	if 5000.5 != ps[0] {
+		t.Errorf("median: 5000.5 != %v\n", ps[0])
+	}
+	if 7500.75 != ps[1] {
+		t.Errorf("75th percentile: 7500.75 != %v\n", ps[1])
+	}
+	if 9900.99 != ps[2] {
+		t.Errorf("99th percentile: 9900.99 != %v\n", ps[2])
+	}
+}

sample_test.go

@@ -0,0 +1,71 @@
+package metrics
+
+import (
+	"testing"
+)
+
+// <https://github.com/codahale/metrics/blob/development/metrics-core/src/test/java/com/yammer/metrics/stats/tests/ExponentiallyDecayingSampleTest.java>
+
+func TestExpDecaySample10(t *testing.T) {
+	s := NewExpDecaySample(100, 0.99)
+	for i := 0; i < 10; i++ { s.Update(int64(i)) }
+	if size := s.Size(); 10 != size {
+		t.Errorf("s.Size(): 10 != %v\n", size)
+	}
+	if l := len(s.Values()); 10 != l {
+		t.Errorf("len(s.Values()): 10 != %v\n", l)
+	}
+	for _, v := range s.Values() {
+		if v > 10 || v < 0 {
+			t.Errorf("out of range [0, 10): %v\n", v)
+		}
+	}
+}
+
+func TestExpDecaySample100(t *testing.T) {
+	s := NewExpDecaySample(1000, 0.01)
+	for i := 0; i < 100; i++ { s.Update(int64(i)) }
+	if size := s.Size(); 100 != size {
+		t.Errorf("s.Size(): 100 != %v\n", size)
+	}
+	if l := len(s.Values()); 100 != l {
+		t.Errorf("len(s.Values()): 100 != %v\n", l)
+	}
+	for _, v := range s.Values() {
+		if v > 100 || v < 0 {
+			t.Errorf("out of range [0, 100): %v\n", v)
+		}
+	}
+}
+
+func TestExpDecaySample1000(t *testing.T) {
+	s := NewExpDecaySample(100, 0.99)
+	for i := 0; i < 1000; i++ { s.Update(int64(i)) }
+	if size := s.Size(); 100 != size {
+		t.Errorf("s.Size(): 100 != %v\n", size)
+	}
+	if l := len(s.Values()); 100 != l {
+		t.Errorf("len(s.Values()): 100 != %v\n", l)
+	}
+	for _, v := range s.Values() {
+		if v > 1000 || v < 0 {
+			t.Errorf("out of range [0, 100): %v\n", v)
+		}
+	}
+}
+
+func TestUniformSample(t *testing.T) {
+	s := NewUniformSample(100)
+	for i := 0; i < 1000; i++ { s.Update(int64(i)) }
+	if size := s.Size(); 100 != size {
+		t.Errorf("s.Size(): 100 != %v\n", size)
+	}
+	if l := len(s.Values()); 100 != l {
+		t.Errorf("len(s.Values()): 100 != %v\n", l)
+	}
+	for _, v := range s.Values() {
+		if v > 1000 || v < 0 {
+			t.Errorf("out of range [0, 100): %v\n", v)
+		}
+	}
+}