Merge pull request #610 from dmcgowan/snapshot-move-testsuite

snapshot: move testsuite to sub-package

snapshot/btrfs/btrfs_test.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/docker/containerd"
 	"github.com/docker/containerd/snapshot"
+	"github.com/docker/containerd/snapshot/testsuite"
 	"github.com/docker/containerd/testutil"
 )
 
@@ -20,7 +21,7 @@ const (
 
 func TestBtrfs(t *testing.T) {
 	testutil.RequiresRoot(t)
-	snapshot.SnapshotterSuite(t, "Btrfs", func(root string) (snapshot.Snapshotter, func(), error) {
+	testsuite.SnapshotterSuite(t, "Btrfs", func(root string) (snapshot.Snapshotter, func(), error) {
 		device := setupBtrfsLoopbackDevice(t, root)
 		snapshotter, err := NewSnapshotter(device.deviceName, root)
 		if err != nil {

snapshot/overlay/overlay_test.go

@@ -11,12 +11,13 @@ import (
 
 	"github.com/docker/containerd"
 	"github.com/docker/containerd/snapshot"
+	"github.com/docker/containerd/snapshot/testsuite"
 	"github.com/docker/containerd/testutil"
 )
 
 func TestOverlay(t *testing.T) {
 	testutil.RequiresRoot(t)
-	snapshot.SnapshotterSuite(t, "Overlay", func(root string) (snapshot.Snapshotter, func(), error) {
+	testsuite.SnapshotterSuite(t, "Overlay", func(root string) (snapshot.Snapshotter, func(), error) {
 		snapshotter, err := NewSnapshotter(root)
 		if err != nil {
 			t.Fatal(err)

snapshot/snapshotter.go

@@ -2,16 +2,8 @@ package snapshot
 
 import (
 	"context"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"syscall"
-	"testing"
 
 	"github.com/docker/containerd"
-	"github.com/docker/containerd/fs/fstest"
-	"github.com/docker/containerd/testutil"
-	"github.com/stretchr/testify/assert"
 )
 
 // Kind identifies the kind of snapshot.
@@ -215,178 +207,3 @@ type Snapshotter interface {
 	// function will be called.
 	Walk(ctx context.Context, fn func(context.Context, Info) error) error
 }
-
-// SnapshotterSuite runs a test suite on the snapshotter given a factory function.
-func SnapshotterSuite(t *testing.T, name string, snapshotterFn func(root string) (Snapshotter, func(), error)) {
-	t.Run("Basic", makeTest(t, name, snapshotterFn, checkSnapshotterBasic))
-	t.Run("StatActive", makeTest(t, name, snapshotterFn, checkSnapshotterStatActive))
-	t.Run("StatComitted", makeTest(t, name, snapshotterFn, checkSnapshotterStatCommitted))
-	t.Run("TransitivityTest", makeTest(t, name, snapshotterFn, checkSnapshotterTransitivity))
-
-}
-
-func makeTest(t *testing.T, name string, snapshotterFn func(root string) (Snapshotter, func(), error), fn func(t *testing.T, snapshotter Snapshotter, work string)) func(t *testing.T) {
-	return func(t *testing.T) {
-		oldumask := syscall.Umask(0)
-		defer syscall.Umask(oldumask)
-		// Make two directories: a snapshotter root and a play area for the tests:
-		//
-		// 	/tmp
-		// 		work/ -> passed to test functions
-		// 		root/ -> passed to snapshotter
-		//
-		tmpDir, err := ioutil.TempDir("", "snapshot-suite-"+name+"-")
-		if err != nil {
-			t.Fatal(err)
-		}
-		defer os.RemoveAll(tmpDir)
-
-		root := filepath.Join(tmpDir, "root")
-		if err := os.MkdirAll(root, 0777); err != nil {
-			t.Fatal(err)
-		}
-
-		snapshotter, cleanup, err := snapshotterFn(root)
-		if err != nil {
-			t.Fatal(err)
-		}
-		defer cleanup()
-
-		work := filepath.Join(tmpDir, "work")
-		if err := os.MkdirAll(work, 0777); err != nil {
-			t.Fatal(err)
-		}
-
-		defer testutil.DumpDir(t, tmpDir)
-		fn(t, snapshotter, work)
-	}
-}
-
-// checkSnapshotterBasic tests the basic workflow of a snapshot snapshotter.
-func checkSnapshotterBasic(t *testing.T, snapshotter Snapshotter, work string) {
-	ctx := context.TODO()
-
-	initialApplier := fstest.Apply(
-		fstest.CreateFile("/foo", []byte("foo\n"), 0777),
-		fstest.CreateDir("/a", 0755),
-		fstest.CreateDir("/a/b", 0755),
-		fstest.CreateDir("/a/b/c", 0755),
-	)
-
-	diffApplier := fstest.Apply(
-		fstest.CreateFile("/bar", []byte("bar\n"), 0777),
-		// also, change content of foo to bar
-		fstest.CreateFile("/foo", []byte("bar\n"), 0777),
-		fstest.RemoveAll("/a/b"),
-	)
-
-	preparing := filepath.Join(work, "preparing")
-	if err := os.MkdirAll(preparing, 0777); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	mounts, err := snapshotter.Prepare(ctx, preparing, "")
-	if err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	if len(mounts) < 1 {
-		t.Fatal("expected mounts to have entries")
-	}
-
-	if err := containerd.MountAll(mounts, preparing); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-	defer testutil.Unmount(t, preparing)
-
-	if err := initialApplier.Apply(preparing); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	committed := filepath.Join(work, "committed")
-	if err := snapshotter.Commit(ctx, committed, preparing); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	si, err := snapshotter.Stat(ctx, committed)
-	if err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	assert.Equal(t, "", si.Parent)
-	assert.Equal(t, KindCommitted, si.Kind)
-
-	next := filepath.Join(work, "nextlayer")
-	if err := os.MkdirAll(next, 0777); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	mounts, err = snapshotter.Prepare(ctx, next, committed)
-	if err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-	if err := containerd.MountAll(mounts, next); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-	defer testutil.Unmount(t, next)
-
-	if err := fstest.CheckDirectoryEqualWithApplier(next, initialApplier); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	if err := diffApplier.Apply(next); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	ni, err := snapshotter.Stat(ctx, next)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	assert.Equal(t, committed, ni.Parent)
-	assert.Equal(t, KindActive, ni.Kind)
-
-	nextCommitted := filepath.Join(work, "committed-next")
-	if err := snapshotter.Commit(ctx, nextCommitted, next); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	si2, err := snapshotter.Stat(ctx, nextCommitted)
-	if err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	assert.Equal(t, committed, si2.Parent)
-	assert.Equal(t, KindCommitted, si2.Kind)
-
-	expected := map[string]Info{
-		si.Name:  si,
-		si2.Name: si2,
-	}
-	walked := map[string]Info{} // walk is not ordered
-	assert.NoError(t, snapshotter.Walk(ctx, func(ctx context.Context, si Info) error {
-		walked[si.Name] = si
-		return nil
-	}))
-
-	assert.Equal(t, expected, walked)
-
-	nextnext := filepath.Join(work, "nextnextlayer")
-	if err := os.MkdirAll(nextnext, 0777); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-
-	mounts, err = snapshotter.View(ctx, nextnext, nextCommitted)
-	if err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-	if err := containerd.MountAll(mounts, nextnext); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-	defer testutil.Unmount(t, nextnext)
-
-	if err := fstest.CheckDirectoryEqualWithApplier(nextnext,
-		fstest.Apply(initialApplier, diffApplier)); err != nil {
-		t.Fatalf("failure reason: %+v", err)
-	}
-}

snapshot/testsuite.go

@@ -1,166 +0,0 @@
-package snapshot
-
-import (
-	"context"
-	"fmt"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"testing"
-
-	"github.com/docker/containerd"
-	"github.com/docker/containerd/testutil"
-	"github.com/stretchr/testify/assert"
-)
-
-// Create a New Layer on top of base layer with Prepare, Stat on new layer, should return Active layer.
-func checkSnapshotterStatActive(t *testing.T, snapshotter Snapshotter, work string) {
-	ctx := context.TODO()
-	preparing := filepath.Join(work, "preparing")
-	if err := os.MkdirAll(preparing, 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	mounts, err := snapshotter.Prepare(ctx, preparing, "")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if len(mounts) < 1 {
-		t.Fatal("expected mounts to have entries")
-	}
-
-	if err = containerd.MountAll(mounts, preparing); err != nil {
-		t.Fatal(err)
-	}
-	defer testutil.Unmount(t, preparing)
-
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	si, err := snapshotter.Stat(ctx, preparing)
-	if err != nil {
-		t.Fatal(err)
-	}
-	assert.Equal(t, si.Name, preparing)
-	assert.Equal(t, KindActive, si.Kind)
-	assert.Equal(t, "", si.Parent)
-}
-
-// Commit a New Layer on top of base layer with Prepare & Commit , Stat on new layer, should return Committed layer.
-func checkSnapshotterStatCommitted(t *testing.T, snapshotter Snapshotter, work string) {
-	ctx := context.TODO()
-	preparing := filepath.Join(work, "preparing")
-	if err := os.MkdirAll(preparing, 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	mounts, err := snapshotter.Prepare(ctx, preparing, "")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if len(mounts) < 1 {
-		t.Fatal("expected mounts to have entries")
-	}
-
-	if err = containerd.MountAll(mounts, preparing); err != nil {
-		t.Fatal(err)
-	}
-	defer testutil.Unmount(t, preparing)
-
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	committed := filepath.Join(work, "committed")
-	if err = snapshotter.Commit(ctx, committed, preparing); err != nil {
-		t.Fatal(err)
-	}
-
-	si, err := snapshotter.Stat(ctx, committed)
-	if err != nil {
-		t.Fatal(err)
-	}
-	assert.Equal(t, si.Name, committed)
-	assert.Equal(t, KindCommitted, si.Kind)
-	assert.Equal(t, "", si.Parent)
-
-}
-
-func snapshotterPrepareMount(ctx context.Context, snapshotter Snapshotter, diffPathName string, parent string, work string) (string, error) {
-	preparing := filepath.Join(work, diffPathName)
-	if err := os.MkdirAll(preparing, 0777); err != nil {
-		return "", err
-	}
-
-	mounts, err := snapshotter.Prepare(ctx, preparing, parent)
-	if err != nil {
-		return "", err
-	}
-
-	if len(mounts) < 1 {
-		return "", fmt.Errorf("expected mounts to have entries")
-	}
-
-	if err = containerd.MountAll(mounts, preparing); err != nil {
-		return "", err
-	}
-	return preparing, nil
-}
-
-// Given A <- B <- C, B is the parent of C and A is a transitive parent of C (in this case, a "grandparent")
-func checkSnapshotterTransitivity(t *testing.T, snapshotter Snapshotter, work string) {
-	ctx := context.TODO()
-	preparing, err := snapshotterPrepareMount(ctx, snapshotter, "preparing", "", work)
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testutil.Unmount(t, preparing)
-
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	snapA := filepath.Join(work, "snapA")
-	if err = snapshotter.Commit(ctx, snapA, preparing); err != nil {
-		t.Fatal(err)
-	}
-
-	next, err := snapshotterPrepareMount(ctx, snapshotter, "next", snapA, work)
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testutil.Unmount(t, next)
-
-	if err = ioutil.WriteFile(filepath.Join(next, "foo"), []byte("foo bar\n"), 0777); err != nil {
-		t.Fatal(err)
-	}
-
-	snapB := filepath.Join(work, "snapB")
-	if err = snapshotter.Commit(ctx, snapB, next); err != nil {
-		t.Fatal(err)
-	}
-
-	siA, err := snapshotter.Stat(ctx, snapA)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	siB, err := snapshotter.Stat(ctx, snapB)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	siParentB, err := snapshotter.Stat(ctx, siB.Parent)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Test the transivity
-	assert.Equal(t, "", siA.Parent)
-	assert.Equal(t, snapA, siB.Parent)
-	assert.Equal(t, "", siParentB.Parent)
-
-}

snapshot/testsuite/testsuite.go

@@ -0,0 +1,344 @@
+package testsuite
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+
+	"github.com/docker/containerd"
+	"github.com/docker/containerd/fs/fstest"
+	"github.com/docker/containerd/snapshot"
+	"github.com/docker/containerd/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+// SnapshotterSuite runs a test suite on the snapshotter given a factory function.
+func SnapshotterSuite(t *testing.T, name string, snapshotterFn func(root string) (snapshot.Snapshotter, func(), error)) {
+	t.Run("Basic", makeTest(t, name, snapshotterFn, checkSnapshotterBasic))
+	t.Run("StatActive", makeTest(t, name, snapshotterFn, checkSnapshotterStatActive))
+	t.Run("StatComitted", makeTest(t, name, snapshotterFn, checkSnapshotterStatCommitted))
+	t.Run("TransitivityTest", makeTest(t, name, snapshotterFn, checkSnapshotterTransitivity))
+
+}
+
+func makeTest(t *testing.T, name string, snapshotterFn func(root string) (snapshot.Snapshotter, func(), error), fn func(t *testing.T, snapshotter snapshot.Snapshotter, work string)) func(t *testing.T) {
+	return func(t *testing.T) {
+		oldumask := syscall.Umask(0)
+		defer syscall.Umask(oldumask)
+		// Make two directories: a snapshotter root and a play area for the tests:
+		//
+		// 	/tmp
+		// 		work/ -> passed to test functions
+		// 		root/ -> passed to snapshotter
+		//
+		tmpDir, err := ioutil.TempDir("", "snapshot-suite-"+name+"-")
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer os.RemoveAll(tmpDir)
+
+		root := filepath.Join(tmpDir, "root")
+		if err := os.MkdirAll(root, 0777); err != nil {
+			t.Fatal(err)
+		}
+
+		snapshotter, cleanup, err := snapshotterFn(root)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer cleanup()
+
+		work := filepath.Join(tmpDir, "work")
+		if err := os.MkdirAll(work, 0777); err != nil {
+			t.Fatal(err)
+		}
+
+		defer testutil.DumpDir(t, tmpDir)
+		fn(t, snapshotter, work)
+	}
+}
+
+// checkSnapshotterBasic tests the basic workflow of a snapshot snapshotter.
+func checkSnapshotterBasic(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+	ctx := context.TODO()
+
+	initialApplier := fstest.Apply(
+		fstest.CreateFile("/foo", []byte("foo\n"), 0777),
+		fstest.CreateDir("/a", 0755),
+		fstest.CreateDir("/a/b", 0755),
+		fstest.CreateDir("/a/b/c", 0755),
+	)
+
+	diffApplier := fstest.Apply(
+		fstest.CreateFile("/bar", []byte("bar\n"), 0777),
+		// also, change content of foo to bar
+		fstest.CreateFile("/foo", []byte("bar\n"), 0777),
+		fstest.RemoveAll("/a/b"),
+	)
+
+	preparing := filepath.Join(work, "preparing")
+	if err := os.MkdirAll(preparing, 0777); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	mounts, err := snapshotter.Prepare(ctx, preparing, "")
+	if err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	if len(mounts) < 1 {
+		t.Fatal("expected mounts to have entries")
+	}
+
+	if err := containerd.MountAll(mounts, preparing); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+	defer testutil.Unmount(t, preparing)
+
+	if err := initialApplier.Apply(preparing); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	committed := filepath.Join(work, "committed")
+	if err := snapshotter.Commit(ctx, committed, preparing); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	si, err := snapshotter.Stat(ctx, committed)
+	if err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	assert.Equal(t, "", si.Parent)
+	assert.Equal(t, snapshot.KindCommitted, si.Kind)
+
+	next := filepath.Join(work, "nextlayer")
+	if err := os.MkdirAll(next, 0777); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	mounts, err = snapshotter.Prepare(ctx, next, committed)
+	if err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+	if err := containerd.MountAll(mounts, next); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+	defer testutil.Unmount(t, next)
+
+	if err := fstest.CheckDirectoryEqualWithApplier(next, initialApplier); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	if err := diffApplier.Apply(next); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	ni, err := snapshotter.Stat(ctx, next)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, committed, ni.Parent)
+	assert.Equal(t, snapshot.KindActive, ni.Kind)
+
+	nextCommitted := filepath.Join(work, "committed-next")
+	if err := snapshotter.Commit(ctx, nextCommitted, next); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	si2, err := snapshotter.Stat(ctx, nextCommitted)
+	if err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	assert.Equal(t, committed, si2.Parent)
+	assert.Equal(t, snapshot.KindCommitted, si2.Kind)
+
+	expected := map[string]snapshot.Info{
+		si.Name:  si,
+		si2.Name: si2,
+	}
+	walked := map[string]snapshot.Info{} // walk is not ordered
+	assert.NoError(t, snapshotter.Walk(ctx, func(ctx context.Context, si snapshot.Info) error {
+		walked[si.Name] = si
+		return nil
+	}))
+
+	assert.Equal(t, expected, walked)
+
+	nextnext := filepath.Join(work, "nextnextlayer")
+	if err := os.MkdirAll(nextnext, 0777); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+
+	mounts, err = snapshotter.View(ctx, nextnext, nextCommitted)
+	if err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+	if err := containerd.MountAll(mounts, nextnext); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+	defer testutil.Unmount(t, nextnext)
+
+	if err := fstest.CheckDirectoryEqualWithApplier(nextnext,
+		fstest.Apply(initialApplier, diffApplier)); err != nil {
+		t.Fatalf("failure reason: %+v", err)
+	}
+}
+
+// Create a New Layer on top of base layer with Prepare, Stat on new layer, should return Active layer.
+func checkSnapshotterStatActive(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+	ctx := context.TODO()
+	preparing := filepath.Join(work, "preparing")
+	if err := os.MkdirAll(preparing, 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	mounts, err := snapshotter.Prepare(ctx, preparing, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(mounts) < 1 {
+		t.Fatal("expected mounts to have entries")
+	}
+
+	if err = containerd.MountAll(mounts, preparing); err != nil {
+		t.Fatal(err)
+	}
+	defer testutil.Unmount(t, preparing)
+
+	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	si, err := snapshotter.Stat(ctx, preparing)
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, si.Name, preparing)
+	assert.Equal(t, snapshot.KindActive, si.Kind)
+	assert.Equal(t, "", si.Parent)
+}
+
+// Commit a New Layer on top of base layer with Prepare & Commit , Stat on new layer, should return Committed layer.
+func checkSnapshotterStatCommitted(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+	ctx := context.TODO()
+	preparing := filepath.Join(work, "preparing")
+	if err := os.MkdirAll(preparing, 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	mounts, err := snapshotter.Prepare(ctx, preparing, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(mounts) < 1 {
+		t.Fatal("expected mounts to have entries")
+	}
+
+	if err = containerd.MountAll(mounts, preparing); err != nil {
+		t.Fatal(err)
+	}
+	defer testutil.Unmount(t, preparing)
+
+	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	committed := filepath.Join(work, "committed")
+	if err = snapshotter.Commit(ctx, committed, preparing); err != nil {
+		t.Fatal(err)
+	}
+
+	si, err := snapshotter.Stat(ctx, committed)
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, si.Name, committed)
+	assert.Equal(t, snapshot.KindCommitted, si.Kind)
+	assert.Equal(t, "", si.Parent)
+
+}
+
+func snapshotterPrepareMount(ctx context.Context, snapshotter snapshot.Snapshotter, diffPathName string, parent string, work string) (string, error) {
+	preparing := filepath.Join(work, diffPathName)
+	if err := os.MkdirAll(preparing, 0777); err != nil {
+		return "", err
+	}
+
+	mounts, err := snapshotter.Prepare(ctx, preparing, parent)
+	if err != nil {
+		return "", err
+	}
+
+	if len(mounts) < 1 {
+		return "", fmt.Errorf("expected mounts to have entries")
+	}
+
+	if err = containerd.MountAll(mounts, preparing); err != nil {
+		return "", err
+	}
+	return preparing, nil
+}
+
+// Given A <- B <- C, B is the parent of C and A is a transitive parent of C (in this case, a "grandparent")
+func checkSnapshotterTransitivity(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+	ctx := context.TODO()
+	preparing, err := snapshotterPrepareMount(ctx, snapshotter, "preparing", "", work)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer testutil.Unmount(t, preparing)
+
+	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	snapA := filepath.Join(work, "snapA")
+	if err = snapshotter.Commit(ctx, snapA, preparing); err != nil {
+		t.Fatal(err)
+	}
+
+	next, err := snapshotterPrepareMount(ctx, snapshotter, "next", snapA, work)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer testutil.Unmount(t, next)
+
+	if err = ioutil.WriteFile(filepath.Join(next, "foo"), []byte("foo bar\n"), 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	snapB := filepath.Join(work, "snapB")
+	if err = snapshotter.Commit(ctx, snapB, next); err != nil {
+		t.Fatal(err)
+	}
+
+	siA, err := snapshotter.Stat(ctx, snapA)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	siB, err := snapshotter.Stat(ctx, snapB)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	siParentB, err := snapshotter.Stat(ctx, siB.Parent)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Test the transivity
+	assert.Equal(t, "", siA.Parent)
+	assert.Equal(t, snapA, siB.Parent)
+	assert.Equal(t, "", siParentB.Parent)
+
+}