diff --git a/doorcontrol/hid/tests/__init__.py b/doorcontrol/hid/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/doorcontrol/hid/tests/test_Credential.py b/doorcontrol/hid/tests/test_Credential.py
new file mode 100644
index 0000000..7e9b240
--- /dev/null
+++ b/doorcontrol/hid/tests/test_Credential.py
@@ -0,0 +1,20 @@
+from unittest import TestCase
+
+from hypothesis import given
+from hypothesis import strategies as st
+
+from doorcontrol.hid.Credential import Credential
+
+
+class CredentialTestCase(TestCase):
+    @given(facility_code=st.integers(0, 0xFF), card_number=st.integers(0, 0xFFFF))
+    def test_code_round_trip(self, facility_code: int, card_number: int):
+        cred = Credential.from_code(facility_code, card_number)
+        self.assertEqual(cred.facility_code, facility_code)
+        self.assertEqual(cred.card_number, card_number)
+
+    @given(facility_code=st.integers(0, 0xFF), card_number=st.integers(0, 0xFFFF))
+    def test_to_hex_round_trip(self, facility_code: int, card_number: int):
+        cred = Credential.from_code(facility_code, card_number)
+        hex_cred = Credential.from_hex(cred.hex)
+        self.assertEqual(cred, hex_cred)