diff --git a/states/statemgr/statemgr_fake.go b/states/statemgr/statemgr_fake.go
index 42d2b9bb3..36de10865 100644
--- a/states/statemgr/statemgr_fake.go
+++ b/states/statemgr/statemgr_fake.go
@@ -94,3 +94,39 @@ func (m *fakeFull) Unlock(id string) error {
 	m.locked = false
 	return nil
 }
+
+// NewUnlockErrorFull returns a state manager that is useful for testing errors
+// (mostly Unlock errors) when used with the clistate.Locker interface. Lock()
+// does not return an error because clistate.Locker Lock()s the state at the
+// start of Unlock(), so Lock() must succeeded for Unlock() to get called.
+func NewUnlockErrorFull(t Transient, initial *states.State) Full {
+	return &fakeErrorFull{}
+}
+
+type fakeErrorFull struct{}
+
+var _ Full = (*fakeErrorFull)(nil)
+
+func (m *fakeErrorFull) State() *states.State {
+	return nil
+}
+
+func (m *fakeErrorFull) WriteState(s *states.State) error {
+	return errors.New("fake state manager error")
+}
+
+func (m *fakeErrorFull) RefreshState() error {
+	return errors.New("fake state manager error")
+}
+
+func (m *fakeErrorFull) PersistState() error {
+	return errors.New("fake state manager error")
+}
+
+func (m *fakeErrorFull) Lock(info *LockInfo) (string, error) {
+	return "placeholder", nil
+}
+
+func (m *fakeErrorFull) Unlock(id string) error {
+	return errors.New("fake state manager error")
+}