diff --git a/rootfs/rootfstest/BUILD b/internal/tartest/BUILD
similarity index 73%
rename from rootfs/rootfstest/BUILD
rename to internal/tartest/BUILD
index 113a9d5..72b2532 100644
--- a/rootfs/rootfstest/BUILD
+++ b/internal/tartest/BUILD
@@ -2,15 +2,15 @@ load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "go_default_library",
-    srcs = ["rootfstest.go"],
-    importpath = "github.com/motiejus/code/undocker/rootfs/rootfstest",
+    srcs = ["tartest.go"],
+    importpath = "github.com/motiejus/code/undocker/internal/tartest",
     visibility = ["//visibility:public"],
     deps = ["@com_github_stretchr_testify//require:go_default_library"],
 )
 
 go_test(
     name = "go_default_test",
-    srcs = ["rootfstest_test.go"],
+    srcs = ["tartest_test.go"],
     embed = [":go_default_library"],
     deps = ["@com_github_stretchr_testify//assert:go_default_library"],
 )
diff --git a/rootfs/rootfstest/rootfstest.go b/internal/tartest/tartest.go
similarity index 85%
rename from rootfs/rootfstest/rootfstest.go
rename to internal/tartest/tartest.go
index e9b7063..6b1bb72 100644
--- a/rootfs/rootfstest/rootfstest.go
+++ b/internal/tartest/tartest.go
@@ -1,9 +1,8 @@
-package rootfstest
+package tartest
 
 import (
 	"archive/tar"
 	"bytes"
-	"encoding/json"
 	"io"
 	"testing"
 
@@ -32,16 +31,10 @@ type (
 		Contents *bytes.Buffer
 	}
 
-	Manifest []string
-
 	Hardlink struct {
 		Name string
 		Uid  int
 	}
-
-	dockerManifestJSON []struct {
-		Layers []string `json:"Layers"`
-	}
 )
 
 func (tb Tarball) Buffer() *bytes.Buffer {
@@ -85,17 +78,6 @@ func (f File) Tar(tw *tar.Writer) error {
 	return nil
 }
 
-func (m Manifest) Tar(tw *tar.Writer) error {
-	b, err := json.Marshal(dockerManifestJSON{{Layers: m}})
-	if err != nil {
-		return err
-	}
-	return File{
-		Name:     "manifest.json",
-		Contents: bytes.NewBuffer(b),
-	}.Tar(tw)
-}
-
 func (h Hardlink) Tar(tw *tar.Writer) error {
 	return tw.WriteHeader(&tar.Header{
 		Typeflag: tar.TypeLink,
diff --git a/rootfs/rootfstest/rootfstest_test.go b/internal/tartest/tartest_test.go
similarity index 97%
rename from rootfs/rootfstest/rootfstest_test.go
rename to internal/tartest/tartest_test.go
index f6c7d1c..5596ef8 100644
--- a/rootfs/rootfstest/rootfstest_test.go
+++ b/internal/tartest/tartest_test.go
@@ -1,4 +1,4 @@
-package rootfstest
+package tartest
 
 import (
 	"bytes"
diff --git a/rootfs/BUILD b/rootfs/BUILD
index f366c67..978f0b9 100644
--- a/rootfs/BUILD
+++ b/rootfs/BUILD
@@ -20,7 +20,7 @@ go_test(
     ],
     embed = [":go_default_library"],
     deps = [
-        "//src/undocker/rootfs/rootfstest:go_default_library",
+        "//src/undocker/internal/tartest:go_default_library",
         "@com_github_stretchr_testify//assert:go_default_library",
         "@com_github_stretchr_testify//require:go_default_library",
     ],
diff --git a/rootfs/rootfs_test.go b/rootfs/rootfs_test.go
index 8353f3a..bc9acd1 100644
--- a/rootfs/rootfs_test.go
+++ b/rootfs/rootfs_test.go
@@ -1,25 +1,22 @@
 package rootfs
 
 import (
+	"archive/tar"
 	"bytes"
+	"encoding/json"
 	"testing"
 
-	"github.com/motiejus/code/undocker/rootfs/rootfstest"
+	"github.com/motiejus/code/undocker/internal/tartest"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
 type (
-	file        = rootfstest.File
-	dir         = rootfstest.Dir
-	hardlink    = rootfstest.Hardlink
-	manifest    = rootfstest.Manifest
-	extractable = rootfstest.Extractable
-	tarball     = rootfstest.Tarball
-)
-
-var (
-	extract = rootfstest.Extract
+	file        = tartest.File
+	dir         = tartest.Dir
+	hardlink    = tartest.Hardlink
+	extractable = tartest.Extractable
+	tarball     = tartest.Tarball
 )
 
 func TestRootFS(t *testing.T) {
@@ -183,8 +180,24 @@ func TestRootFS(t *testing.T) {
 				return
 			}
 			require.NoError(t, err)
-			got := extract(t, &out)
+			got := tartest.Extract(t, &out)
 			assert.Equal(t, tt.want, got)
 		})
 	}
 }
+
+// Helpers
+type (
+	manifest []string
+)
+
+func (m manifest) Tar(tw *tar.Writer) error {
+	b, err := json.Marshal(dockerManifestJSON{{Layers: m}})
+	if err != nil {
+		return err
+	}
+	return file{
+		Name:     "manifest.json",
+		Contents: bytes.NewBuffer(b),
+	}.Tar(tw)
+}
diff --git a/rootfs/tree.go b/rootfs/tree.go
index 6c7a7a0..50079c9 100644
--- a/rootfs/tree.go
+++ b/rootfs/tree.go
@@ -15,7 +15,7 @@ type tree struct {
 	end      bool
 }
 
-// New creates a new tree from a given path.
+// newTree creates a new tree from a given path.
 func newTree(paths ...string) *tree {
 	t := &tree{name: ".", children: []*tree{}}
 	for _, path := range paths {