@@ -14,7 +14,7 @@ import (

 	"github.com/docker/docker/integration-cli/cli/build/fakecontext"

 	"github.com/docker/docker/integration-cli/request"

 	"github.com/docker/docker/internal/test/environment"

-	"github.com/docker/docker/pkg/stringutils"

+	"github.com/docker/docker/internal/testutil"

 	"github.com/stretchr/testify/require"

 )

@@ -124,8 +124,8 @@ func (f *remoteFileServer) Close() error {

 func newRemoteFileServer(t testingT, ctx *fakecontext.Fake) *remoteFileServer {

 	var (

-		image     = fmt.Sprintf("fileserver-img-%s", strings.ToLower(stringutils.GenerateRandomAlphaOnlyString(10)))

-		container = fmt.Sprintf("fileserver-cnt-%s", strings.ToLower(stringutils.GenerateRandomAlphaOnlyString(10)))

+		image     = fmt.Sprintf("fileserver-img-%s", strings.ToLower(testutil.GenerateRandomAlphaOnlyString(10)))

+		container = fmt.Sprintf("fileserver-cnt-%s", strings.ToLower(testutil.GenerateRandomAlphaOnlyString(10)))

 	)

 	ensureHTTPServerImage(t)

@@ -23,8 +23,8 @@ import (

 	"github.com/docker/docker/integration-cli/cli/build/fakecontext"

 	"github.com/docker/docker/integration-cli/cli/build/fakegit"

 	"github.com/docker/docker/integration-cli/cli/build/fakestorage"

+	"github.com/docker/docker/internal/testutil"

 	"github.com/docker/docker/pkg/archive"

-	"github.com/docker/docker/pkg/stringutils"

 	"github.com/go-check/check"

 	"github.com/gotestyourself/gotestyourself/icmd"

 	digest "github.com/opencontainers/go-digest"

@@ -3185,7 +3185,7 @@ func (s *DockerSuite) TestBuildOnBuildOutput(c *check.C) {

 // FIXME(vdemeester) should be a unit test

 func (s *DockerSuite) TestBuildInvalidTag(c *check.C) {

-	name := "abcd:" + stringutils.GenerateRandomAlphaOnlyString(200)

+	name := "abcd:" + testutil.GenerateRandomAlphaOnlyString(200)

 	buildImage(name, build.WithDockerfile("FROM "+minimalBaseImage()+"\nMAINTAINER quux\n")).Assert(c, icmd.Expected{

 		ExitCode: 125,

 		Err:      "invalid reference format",

@@ -26,10 +26,10 @@ import (

 	"github.com/docker/docker/integration-cli/cli"

 	"github.com/docker/docker/integration-cli/cli/build"

 	"github.com/docker/docker/integration-cli/cli/build/fakecontext"

+	"github.com/docker/docker/internal/testutil"

 	"github.com/docker/docker/pkg/mount"

 	"github.com/docker/docker/pkg/parsers/kernel"

 	"github.com/docker/docker/pkg/stringid"

-	"github.com/docker/docker/pkg/stringutils"

 	"github.com/docker/docker/runconfig"

 	"github.com/docker/go-connections/nat"

 	"github.com/docker/libnetwork/resolvconf"

@@ -1828,7 +1828,7 @@ func testRunWriteSpecialFilesAndNotCommit(c *check.C, name, path string) {

 }

 func eqToBaseDiff(out string, c *check.C) bool {

-	name := "eqToBaseDiff" + stringutils.GenerateRandomAlphaOnlyString(32)

+	name := "eqToBaseDiff" + testutil.GenerateRandomAlphaOnlyString(32)

 	dockerCmd(c, "run", "--name", name, "busybox", "echo", "hello")

 	cID := getIDByName(c, name)

 	baseDiff, _ := dockerCmd(c, "diff", cID)

@@ -6,8 +6,8 @@ import (

 	"github.com/docker/docker/integration-cli/checker"

 	"github.com/docker/docker/integration-cli/cli/build"

+	"github.com/docker/docker/internal/testutil"

 	"github.com/docker/docker/pkg/stringid"

-	"github.com/docker/docker/pkg/stringutils"

 	"github.com/go-check/check"

 )

@@ -34,7 +34,7 @@ func (s *DockerSuite) TestTagInvalidUnprefixedRepo(c *check.C) {

 // ensure we don't allow the use of invalid tags; these tag operations should fail

 func (s *DockerSuite) TestTagInvalidPrefixedRepo(c *check.C) {

-	longTag := stringutils.GenerateRandomAlphaOnlyString(121)

+	longTag := testutil.GenerateRandomAlphaOnlyString(121)

 	invalidTags := []string{"repo:fo$z$", "repo:Foo@3cc", "repo:Foo$3", "repo:Foo*3", "repo:Fo^3", "repo:Foo!3", "repo:%goodbye", "repo:#hashtagit", "repo:F)xcz(", "repo:-foo", "repo:..", longTag}

@@ -7,7 +7,7 @@ import (

 	"path/filepath"

 	"strings"

-	"github.com/docker/docker/pkg/stringutils"

+	"github.com/docker/docker/internal/testutil"

 	"github.com/go-check/check"

 	"github.com/gotestyourself/gotestyourself/icmd"

 	"github.com/pkg/errors"

@@ -60,7 +60,7 @@ func RandomTmpDirPath(s string, platform string) string {

 	if platform == "windows" {

 		tmp = os.Getenv("TEMP")

 	}

-	path := filepath.Join(tmp, fmt.Sprintf("%s.%s", s, stringutils.GenerateRandomAlphaOnlyString(10)))

+	path := filepath.Join(tmp, fmt.Sprintf("%s.%s", s, testutil.GenerateRandomAlphaOnlyString(10)))

 	if platform == "windows" {

 		return filepath.FromSlash(path) // Using \

 	}

new file mode 100644

@@ -0,0 +1,14 @@

+package testutil

+

+import "math/rand"

+

+// GenerateRandomAlphaOnlyString generates an alphabetical random string with length n.

+func GenerateRandomAlphaOnlyString(n int) string {

+	// make a really long string

+	letters := []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

+	b := make([]byte, n)

+	for i := range b {

+		b[i] = letters[rand.Intn(len(letters))]

+	}

+	return string(b)

+}

new file mode 100644

@@ -0,0 +1,33 @@

+package testutil

+

+import (

+	"testing"

+

+	"github.com/stretchr/testify/assert"

+)

+

+func testLengthHelper(generator func(int) string, t *testing.T) {

+	expectedLength := 20

+	s := generator(expectedLength)

+	assert.Equal(t, expectedLength, len(s))

+}

+

+func testUniquenessHelper(generator func(int) string, t *testing.T) {

+	repeats := 25

+	set := make(map[string]struct{}, repeats)

+	for i := 0; i < repeats; i = i + 1 {

+		str := generator(64)

+		assert.Equal(t, 64, len(str))

+		_, ok := set[str]

+		assert.False(t, ok, "Random number is repeated")

+		set[str] = struct{}{}

+	}

+}

+

+func TestGenerateRandomAlphaOnlyStringLength(t *testing.T) {

+	testLengthHelper(GenerateRandomAlphaOnlyString, t)

+}

+

+func TestGenerateRandomAlphaOnlyStringUniqueness(t *testing.T) {

+	testUniquenessHelper(GenerateRandomAlphaOnlyString, t)

+}

@@ -7,17 +7,6 @@ import (

 	"strings"

 )

-// GenerateRandomAlphaOnlyString generates an alphabetical random string with length n.

-func GenerateRandomAlphaOnlyString(n int) string {

-	// make a really long string

-	letters := []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

-	b := make([]byte, n)

-	for i := range b {

-		b[i] = letters[rand.Intn(len(letters))]

-	}

-	return string(b)

-}

-

 // GenerateRandomASCIIString generates an ASCII random string with length n.

 func GenerateRandomASCIIString(n int) string {

 	chars := "abcdefghijklmnopqrstuvwxyz" +

@@ -34,14 +34,6 @@ func isASCII(s string) bool {

 	return true

 }

-func TestGenerateRandomAlphaOnlyStringLength(t *testing.T) {

-	testLengthHelper(GenerateRandomAlphaOnlyString, t)

-}

-

-func TestGenerateRandomAlphaOnlyStringUniqueness(t *testing.T) {

-	testUniquenessHelper(GenerateRandomAlphaOnlyString, t)

-}

-

 func TestGenerateRandomAsciiStringLength(t *testing.T) {

 	testLengthHelper(GenerateRandomASCIIString, t)

 }