plot: Golden test for plot output

lib/plot/plot.go

@@ -88,11 +88,10 @@ func (ls *labeledSeries) add(r *vegeta.Result) (err error) {
 		ls.began = r.Timestamp // first point in attack
 	}
 
-	// found successor
-	for {
+	for len(ls.buf) > 0 {
 		p, ok := ls.buf[ls.seq]
 		if !ok {
-			return nil
+			break
 		}
 		delete(ls.buf, ls.seq)
 
@@ -104,6 +103,8 @@ func (ls *labeledSeries) add(r *vegeta.Result) (err error) {
 
 		ls.seq++
 	}
+
+	return nil
 }
 
 // Opt is a functional option type for Plot.
@@ -127,11 +128,17 @@ func Label(l Labeler) Opt {
 }
 
 // New returns a Plot with the given Opts applied.
+// If no Label opt is given, ErrorLabeler will be used as default.
 func New(opts ...Opt) *Plot {
 	p := &Plot{series: map[string]*labeledSeries{}}
 	for _, opt := range opts {
 		opt(p)
 	}
+
+	if p.label == nil {
+		p.label = ErrorLabeler
+	}
+
 	return p
 }
 
@@ -149,9 +156,7 @@ func (p *Plot) Add(r *vegeta.Result) error {
 func (p *Plot) Close() {
 	for _, as := range p.series {
 		for _, ts := range as.series {
-			if ts != nil {
-				ts.data.Finish()
-			}
+			ts.data.Finish()
 		}
 	}
 }

lib/plot/plot_test.go

@@ -1,15 +1,70 @@
 package plot
 
 import (
+	"bytes"
+	"flag"
 	"io/ioutil"
 	"math/rand"
+	"path/filepath"
 	"testing"
 	"time"
 
 	vegeta "github.com/tsenart/vegeta/lib"
 )
 
+var update = flag.Bool("update", false, "Update .golden files")
+
+func TestPlot(t *testing.T) {
+	p := New(Title("TestPlot"), Downsample(400))
+
+	rng := rand.New(rand.NewSource(0))
+	zf := rand.NewZipf(rng, 3, 2, 1000)
+	attacks := []string{"500QPS", "1000QPS", "2000QPS"}
+	began := time.Now()
+	for i := 0; i < 1e5; i++ {
+		for _, attack := range attacks {
+			r := vegeta.Result{
+				Attack:    attack,
+				Seq:       uint64(i),
+				Timestamp: began.Add(time.Duration(i) * time.Millisecond),
+				Latency:   time.Duration(zf.Uint64()) * time.Millisecond,
+			}
+
+			if err := p.Add(&r); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+
+	p.Close()
+
+	var b bytes.Buffer
+	if _, err := p.WriteTo(&b); err != nil {
+		t.Fatal(err)
+	}
+
+	gp := filepath.Join("testdata", filepath.FromSlash(t.Name())+".golden.html")
+	if *update {
+		t.Logf("updating %q", gp)
+		if err := ioutil.WriteFile(gp, b.Bytes(), 0644); err != nil {
+			t.Fatalf("failed to update %q: %s", gp, err)
+		}
+	}
+
+	g, err := ioutil.ReadFile(gp)
+	if err != nil {
+		t.Fatalf("failed reading %q: %s", gp, err)
+	}
+
+	if !bytes.Equal(b.Bytes(), g) {
+		t.Log(string(b.Bytes()))
+		t.Errorf("bytes do not match %q", gp)
+	}
+}
+
 func TestLabeledSeries(t *testing.T) {
+	t.Parallel()
+
 	s := newLabeledSeries(func(r *vegeta.Result) string {
 		return r.Attack
 	})