diff --git a/integration-cli/cli/build/fakestorage/storage.go b/integration-cli/cli/build/fakestorage/storage.go
index 25cd872..eb03636 100644
--- a/integration-cli/cli/build/fakestorage/storage.go
+++ b/integration-cli/cli/build/fakestorage/storage.go
@@ -14,7 +14,7 @@
 	"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 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)
diff --git a/integration-cli/docker_cli_build_test.go b/integration-cli/docker_cli_build_test.go
index f6ab192..89e62c1 100644
--- a/integration-cli/docker_cli_build_test.go
+++ b/integration-cli/docker_cli_build_test.go
@@ -23,8 +23,8 @@
 	"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 @@
 
 // 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",
diff --git a/integration-cli/docker_cli_run_test.go b/integration-cli/docker_cli_run_test.go
index 8198fde..eb01e34 100644
--- a/integration-cli/docker_cli_run_test.go
+++ b/integration-cli/docker_cli_run_test.go
@@ -26,10 +26,10 @@
 	"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 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)
diff --git a/integration-cli/docker_cli_tag_test.go b/integration-cli/docker_cli_tag_test.go
index 907977f..ee94a9b 100644
--- a/integration-cli/docker_cli_tag_test.go
+++ b/integration-cli/docker_cli_tag_test.go
@@ -6,8 +6,8 @@
 
 	"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 @@
 
 // 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}
 
diff --git a/integration-cli/utils_test.go b/integration-cli/utils_test.go
index d176c7f..1146e1b 100644
--- a/integration-cli/utils_test.go
+++ b/integration-cli/utils_test.go
@@ -7,7 +7,7 @@
 	"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 @@
 	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 \
 	}
diff --git a/internal/testutil/stringutils.go b/internal/testutil/stringutils.go
new file mode 100644
index 0000000..76cf8d8
--- /dev/null
+++ b/internal/testutil/stringutils.go
@@ -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)
+}
diff --git a/internal/testutil/stringutils_test.go b/internal/testutil/stringutils_test.go
new file mode 100644
index 0000000..2985a06
--- /dev/null
+++ b/internal/testutil/stringutils_test.go
@@ -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)
+}
diff --git a/pkg/stringutils/stringutils.go b/pkg/stringutils/stringutils.go
index 8c4c398..b294de2 100644
--- a/pkg/stringutils/stringutils.go
+++ b/pkg/stringutils/stringutils.go
@@ -7,17 +7,6 @@
 	"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" +
diff --git a/pkg/stringutils/stringutils_test.go b/pkg/stringutils/stringutils_test.go
index 8af2bdc..15b3cf8 100644
--- a/pkg/stringutils/stringutils_test.go
+++ b/pkg/stringutils/stringutils_test.go
@@ -34,14 +34,6 @@
 	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)
 }