diff --git a/backend/mock_backend.go b/backend/mock_backend.go
new file mode 100644
index 000000000..92d5521c7
--- /dev/null
+++ b/backend/mock_backend.go
@@ -0,0 +1,97 @@
+package backend
+
+import (
+	"errors"
+	"io"
+)
+
+// MockBackend implements a backend whose functions can be specified. This
+// should only be used for tests.
+type MockBackend struct {
+	CloseFn     func() error
+	CreateFn    func() (Blob, error)
+	GetFn       func(Type, string) (io.ReadCloser, error)
+	GetReaderFn func(Type, string, uint, uint) (io.ReadCloser, error)
+	ListFn      func(Type, <-chan struct{}) <-chan string
+	RemoveFn    func(Type, string) error
+	TestFn      func(Type, string) (bool, error)
+	DeleteFn    func() error
+	LocationFn  func() string
+}
+
+func (m *MockBackend) Close() error {
+	if m.CloseFn == nil {
+		return nil
+	}
+
+	return m.CloseFn()
+}
+
+func (m *MockBackend) Location() string {
+	if m.LocationFn == nil {
+		return ""
+	}
+
+	return m.LocationFn()
+}
+
+func (m *MockBackend) Create() (Blob, error) {
+	if m.CreateFn == nil {
+		return nil, errors.New("not implemented")
+	}
+
+	return m.CreateFn()
+}
+
+func (m *MockBackend) Get(t Type, name string) (io.ReadCloser, error) {
+	if m.GetFn == nil {
+		return nil, errors.New("not implemented")
+	}
+
+	return m.GetFn(t, name)
+}
+
+func (m *MockBackend) GetReader(t Type, name string, offset, len uint) (io.ReadCloser, error) {
+	if m.GetReaderFn == nil {
+		return nil, errors.New("not implemented")
+	}
+
+	return m.GetReaderFn(t, name, offset, len)
+}
+
+func (m *MockBackend) List(t Type, done <-chan struct{}) <-chan string {
+	if m.ListFn == nil {
+		ch := make(chan string)
+		close(ch)
+		return ch
+	}
+
+	return m.ListFn(t, done)
+}
+
+func (m *MockBackend) Remove(t Type, name string) error {
+	if m.RemoveFn == nil {
+		return errors.New("not implemented")
+	}
+
+	return m.RemoveFn(t, name)
+}
+
+func (m *MockBackend) Test(t Type, name string) (bool, error) {
+	if m.TestFn == nil {
+		return false, errors.New("not implemented")
+	}
+
+	return m.TestFn(t, name)
+}
+
+func (m *MockBackend) Delete() error {
+	if m.DeleteFn == nil {
+		return errors.New("not implemented")
+	}
+
+	return m.DeleteFn()
+}
+
+// Make sure that MockBackend implements the backend interface.
+var _ Backend = &MockBackend{}