diff --git a/hsm/limbo_hsm.cpp b/hsm/limbo_hsm.cpp
index 09b2bcd..6ecc049 100644
--- a/hsm/limbo_hsm.cpp
+++ b/hsm/limbo_hsm.cpp
@@ -179,7 +179,7 @@ bool LimboHSM::dispatch(const String &p_event, const Variant &p_cargo) {
 		}
 	}
 
-	if (!event_consumed && p_event == EVENT_FINISHED && !(get_parent()->is_class("LimboState"))) {
+	if (!event_consumed && p_event == EVENT_FINISHED && !(get_parent() && get_parent()->is_class("LimboState"))) {
 		_exit();
 	}
 
diff --git a/tests/limbo_test.h b/tests/limbo_test.h
index cbca952..f47c35f 100644
--- a/tests/limbo_test.h
+++ b/tests/limbo_test.h
@@ -24,10 +24,12 @@ public:
 	int num_callbacks = 0;
 
 	void callback() { num_callbacks += 1; }
+	void callback_delta(double delta) { num_callbacks += 1; }
 
 protected:
 	static void _bind_methods() {
 		ClassDB::bind_method(D_METHOD("callback"), &CallbackCounter::callback);
+		ClassDB::bind_method(D_METHOD("callback_delta", "delta"), &CallbackCounter::callback_delta);
 	}
 };
 
diff --git a/tests/test_hsm.h b/tests/test_hsm.h
new file mode 100644
index 0000000..bc981f5
--- /dev/null
+++ b/tests/test_hsm.h
@@ -0,0 +1,182 @@
+/**
+ * test_hsm.h
+ * =============================================================================
+ * Copyright 2021-2023 Serhii Snitsaruk
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT.
+ * =============================================================================
+ */
+
+#ifndef TEST_HSM_H
+#define TEST_HSM_H
+
+#include "limbo_test.h"
+
+#include "modules/limboai/hsm/limbo_hsm.h"
+#include "modules/limboai/hsm/limbo_state.h"
+
+#include "core/object/object.h"
+#include "core/object/ref_counted.h"
+#include "core/os/memory.h"
+#include "core/variant/variant.h"
+
+namespace TestHSM {
+
+class TestGuard : public RefCounted {
+	GDCLASS(TestGuard, RefCounted);
+
+public:
+	bool permitted_to_enter = false;
+	bool can_enter() { return permitted_to_enter; }
+};
+
+TEST_CASE("[Modules][LimboAI] HSM") {
+	Node *agent = memnew(Node);
+	LimboHSM *hsm = memnew(LimboHSM);
+
+	Ref<CallbackCounter> alpha_entries = memnew(CallbackCounter);
+	Ref<CallbackCounter> alpha_exits = memnew(CallbackCounter);
+	Ref<CallbackCounter> alpha_updates = memnew(CallbackCounter);
+	Ref<CallbackCounter> beta_entries = memnew(CallbackCounter);
+	Ref<CallbackCounter> beta_exits = memnew(CallbackCounter);
+	Ref<CallbackCounter> beta_updates = memnew(CallbackCounter);
+
+	LimboState *state_alpha = memnew(LimboState);
+	state_alpha->call_on_enter(callable_mp(alpha_entries.ptr(), &CallbackCounter::callback));
+	state_alpha->call_on_update(callable_mp(alpha_updates.ptr(), &CallbackCounter::callback_delta));
+	state_alpha->call_on_exit(callable_mp(alpha_exits.ptr(), &CallbackCounter::callback));
+
+	LimboState *state_beta = memnew(LimboState);
+	state_beta->call_on_enter(callable_mp(beta_entries.ptr(), &CallbackCounter::callback));
+	state_beta->call_on_update(callable_mp(beta_updates.ptr(), &CallbackCounter::callback_delta));
+	state_beta->call_on_exit(callable_mp(beta_exits.ptr(), &CallbackCounter::callback));
+
+	hsm->add_child(state_alpha);
+	hsm->add_child(state_beta);
+
+	hsm->add_transition(state_alpha, state_beta, "event_one");
+	hsm->add_transition(state_beta, state_alpha, "event_two");
+
+	hsm->set_initial_state(state_alpha);
+	hsm->initialize(agent);
+	hsm->set_active(true);
+
+	SUBCASE("Test get_root()") {
+		CHECK(state_alpha->get_root() == hsm);
+		CHECK(state_beta->get_root() == hsm);
+		CHECK(hsm->get_root() == hsm);
+	}
+	SUBCASE("Test with basic workflow and transitions") {
+		REQUIRE(hsm->is_active());
+		REQUIRE(hsm->get_active_state() == state_alpha);
+		CHECK(alpha_entries->num_callbacks == 1); // * entered
+		CHECK(alpha_updates->num_callbacks == 0);
+		CHECK(alpha_exits->num_callbacks == 0);
+		CHECK(beta_entries->num_callbacks == 0);
+		CHECK(beta_updates->num_callbacks == 0);
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->update(0.01666);
+		CHECK(alpha_entries->num_callbacks == 1);
+		CHECK(alpha_updates->num_callbacks == 1); // * updated
+		CHECK(alpha_exits->num_callbacks == 0);
+		CHECK(beta_entries->num_callbacks == 0);
+		CHECK(beta_updates->num_callbacks == 0);
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->update(0.01666);
+		CHECK(alpha_entries->num_callbacks == 1);
+		CHECK(alpha_updates->num_callbacks == 2); // * updated x2
+		CHECK(alpha_exits->num_callbacks == 0);
+		CHECK(beta_entries->num_callbacks == 0);
+		CHECK(beta_updates->num_callbacks == 0);
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->dispatch("event_one");
+		REQUIRE(hsm->get_active_state() == state_beta);
+		CHECK(alpha_entries->num_callbacks == 1);
+		CHECK(alpha_updates->num_callbacks == 2);
+		CHECK(alpha_exits->num_callbacks == 1); // * (1) exited
+		CHECK(beta_entries->num_callbacks == 1); // * (2) entered
+		CHECK(beta_updates->num_callbacks == 0);
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->update(0.01666);
+		CHECK(alpha_entries->num_callbacks == 1);
+		CHECK(alpha_updates->num_callbacks == 2);
+		CHECK(alpha_exits->num_callbacks == 1);
+		CHECK(beta_entries->num_callbacks == 1);
+		CHECK(beta_updates->num_callbacks == 1); // * updated
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->update(0.01666);
+		CHECK(alpha_entries->num_callbacks == 1);
+		CHECK(alpha_updates->num_callbacks == 2);
+		CHECK(alpha_exits->num_callbacks == 1);
+		CHECK(beta_entries->num_callbacks == 1);
+		CHECK(beta_updates->num_callbacks == 2); // * updated x2
+		CHECK(beta_exits->num_callbacks == 0);
+
+		hsm->dispatch("event_two");
+		REQUIRE(hsm->get_active_state() == state_alpha);
+		CHECK(alpha_entries->num_callbacks == 2); // * (2) entered
+		CHECK(alpha_updates->num_callbacks == 2);
+		CHECK(alpha_exits->num_callbacks == 1);
+		CHECK(beta_entries->num_callbacks == 1);
+		CHECK(beta_updates->num_callbacks == 2);
+		CHECK(beta_exits->num_callbacks == 1); // * (1) exited
+
+		hsm->update(0.01666);
+		CHECK(alpha_entries->num_callbacks == 2);
+		CHECK(alpha_updates->num_callbacks == 3); // * updated
+		CHECK(alpha_exits->num_callbacks == 1);
+		CHECK(beta_entries->num_callbacks == 1);
+		CHECK(beta_updates->num_callbacks == 2);
+		CHECK(beta_exits->num_callbacks == 1);
+
+		hsm->dispatch(LimboState::EVENT_FINISHED);
+		CHECK(alpha_entries->num_callbacks == 2);
+		CHECK(alpha_updates->num_callbacks == 3);
+		CHECK(alpha_exits->num_callbacks == 2); // * exited
+		CHECK(beta_entries->num_callbacks == 1);
+		CHECK(beta_updates->num_callbacks == 2);
+		CHECK(beta_exits->num_callbacks == 1);
+		CHECK_FALSE(hsm->is_active()); // * not active
+		CHECK(hsm->get_active_state() == nullptr);
+	}
+	SUBCASE("Test transition with guard") {
+		Ref<TestGuard> guard = memnew(TestGuard);
+		state_beta->set_guard(callable_mp(guard.ptr(), &TestGuard::can_enter));
+
+		SUBCASE("When entry is permitted") {
+			guard->permitted_to_enter = true;
+			hsm->dispatch("event_one");
+			CHECK(hsm->get_active_state() == state_beta);
+			CHECK(alpha_exits->num_callbacks == 1);
+			CHECK(beta_entries->num_callbacks == 1);
+		}
+		SUBCASE("When entry is not permitted") {
+			guard->permitted_to_enter = false;
+			hsm->dispatch("event_one");
+			CHECK(hsm->get_active_state() == state_alpha);
+			CHECK(alpha_exits->num_callbacks == 0);
+			CHECK(beta_entries->num_callbacks == 0);
+		}
+	}
+	SUBCASE("When there is no transition for given event") {
+		hsm->dispatch("not_found");
+		CHECK(alpha_exits->num_callbacks == 0);
+		CHECK(beta_entries->num_callbacks == 0);
+		CHECK(hsm->is_active());
+		CHECK(hsm->get_active_state() == state_alpha);
+	}
+
+	memdelete(agent);
+	memdelete(hsm);
+}
+
+} //namespace TestHSM
+
+#endif // TEST_HSM_H