[#17] Add unit tests for the generator

Signed-off-by: Vladimir Domnich <v.domnich@yadro.com>

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/nspcc-dev/neo-go v0.98.2
 	github.com/nspcc-dev/neofs-sdk-go v1.0.0-rc.3.0.20220504192402-12ea1e8d740f
 	github.com/nspcc-dev/tzhash v1.5.2
+	github.com/stretchr/testify v1.7.1
 	go.k6.io/k6 v0.38.2
 )
 
@@ -31,6 +32,7 @@ require (
 	github.com/aws/aws-sdk-go-v2/service/sts v1.16.4 // indirect
 	github.com/aws/smithy-go v1.11.2 // indirect
 	github.com/btcsuite/btcd v0.22.0-beta // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dlclark/regexp2 v1.4.1-0.20201116162257-a2a8dda75c91 // indirect
 	github.com/fatih/color v1.13.0 // indirect
 	github.com/go-sourcemap/sourcemap v2.1.4-0.20211119122758-180fcef48034+incompatible // indirect
@@ -47,6 +49,7 @@ require (
 	github.com/nxadm/tail v1.4.8 // indirect
 	github.com/oxtoacart/bpool v0.0.0-20190530202638-03653db5a59c // indirect
 	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/serenize/snaker v0.0.0-20201027110005-a7ad2135616e // indirect
 	github.com/sirupsen/logrus v1.8.1 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
@@ -61,4 +64,5 @@ require (
 	google.golang.org/grpc v1.45.0 // indirect
 	google.golang.org/protobuf v1.27.1 // indirect
 	gopkg.in/guregu/null.v3 v3.3.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

go.sum

@@ -207,9 +207,11 @@ github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxv
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
+github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
 github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
@@ -315,6 +317,7 @@ github.com/prometheus/procfs v0.0.5/go.mod h1:4A/X28fw3Fc593LaREMrKMqOKvUAntwMDa
 github.com/prometheus/procfs v0.1.3/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
 github.com/prometheus/procfs v0.6.0/go.mod h1:cz+aTbrPOrUb4q7XlbU9ygM+/jj0fzG6c1xBZuNvfVA=
 github.com/rogpeppe/fastuuid v1.2.0/go.mod h1:jVj6XXZzXRy/MSR5jhDC/2q6DgLz+nrA6LYCDYWNEvQ=
+github.com/rogpeppe/go-internal v1.6.1 h1:/FiVV8dS/e+YqF2JvO3yXRFbBLTIuSDkuC7aBOAvL+k=
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
@@ -519,6 +522,7 @@ gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLks
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=

internal/datagen/generator.go

@@ -40,6 +40,9 @@ func init() {
 }
 
 func NewGenerator(vu modules.VU, size int) Generator {
+	if size <= 0 {
+		panic("size should be positive")
+	}
 	return Generator{vu: vu, size: size, buf: nil, offset: 0}
 }
 

internal/datagen/generator_test.go

@@ -0,0 +1,56 @@
+package datagen
+
+import (
+	"testing"
+
+	"github.com/dop251/goja"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.k6.io/k6/js/modulestest"
+)
+
+func TestGenerator(t *testing.T) {
+	vu := &modulestest.VU{
+		RuntimeField: goja.New(),
+	}
+
+	t.Run("fails on negative size", func(t *testing.T) {
+		require.Panics(t, func() {
+			_ = NewGenerator(vu, -1)
+		})
+	})
+
+	t.Run("fails on zero size", func(t *testing.T) {
+		require.Panics(t, func() {
+			_ = NewGenerator(vu, 0)
+		})
+	})
+
+	t.Run("creates slice of specified size", func(t *testing.T) {
+		size := 10
+		g := NewGenerator(vu, size)
+		slice := g.nextSlice()
+		require.Len(t, slice, size)
+	})
+
+	t.Run("creates a different slice on each call", func(t *testing.T) {
+		g := NewGenerator(vu, 1000)
+		slice1 := g.nextSlice()
+		slice2 := g.nextSlice()
+		// Each slice should be unique (assuming that 1000 random bytes will never coincide
+		// to be identical)
+		assert.NotEqual(t, slice1, slice2)
+	})
+
+	t.Run("keeps generating slices after consuming entire tail", func(t *testing.T) {
+		g := NewGenerator(vu, 1000)
+		initialSlice := g.nextSlice()
+		for i := 0; i < TailSize; i++ {
+			g.nextSlice()
+		}
+		// After we looped around our tail and returned to the beginning we should have a
+		// unique slice - not the same as in the beginning
+		sliceAfterTail := g.nextSlice()
+		assert.NotEqual(t, initialSlice, sliceAfterTail)
+	})
+}