Restore the simple test

simple/simple_test.go

@@ -0,0 +1,41 @@
+// Copyright 2019, LightStep Inc.
+
+package simple_test
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/lightstep/varopt/simple"
+	"github.com/stretchr/testify/require"
+)
+
+type iRec int
+
+func TestSimple(t *testing.T) {
+	const (
+		popSize        = 1e6
+		sampleProb     = 0.1
+		sampleSize int = popSize * sampleProb
+		epsilon        = 0.01
+	)
+
+	rnd := rand.New(rand.NewSource(17167))
+
+	ss := simple.New(sampleSize, rnd)
+
+	psum := 0.
+	for i := 0; i < popSize; i++ {
+		ss.Add(iRec(i))
+		psum += float64(i)
+	}
+
+	require.Equal(t, ss.Size(), sampleSize)
+
+	ssum := 0.0
+	for i := 0; i < sampleSize; i++ {
+		ssum += float64(ss.Get(i).(iRec))
+	}
+
+	require.InEpsilon(t, ssum/float64(ss.Size()), psum/popSize, epsilon)
+}

varopt.go

@@ -171,7 +171,7 @@ func (s *Varopt) TotalCount() int {
 }
 
 // Tau returns the current large-weight threshold.  Weights larger
-// than Tau() carry their exact weight int he sample.  See the VarOpt
+// than Tau() carry their exact weight in the sample.  See the VarOpt
 // paper for details.
 func (s *Varopt) Tau() float64 {
 	return s.tau