diff --git a/tests/test_airconditioner_ailp_fac_capabilities.py b/tests/test_airconditioner_ailp_fac_capabilities.py
index 5af0f20..9316c8f 100644
--- a/tests/test_airconditioner_ailp_fac_capabilities.py
+++ b/tests/test_airconditioner_ailp_fac_capabilities.py
@@ -44,6 +44,7 @@ def _resources():
 def _bound():
     resources = _resources()
     reg = resolve(resources, device_types=_DEVICE_TYPES)
+    assert reg is not None
     return discover(resources, reg.capabilities, reg.pattern_capabilities), resources
 
 
@@ -68,6 +69,7 @@ def test_board_token_resolves_to_airconditioner_registry():
 def test_no_unbound_hrefs():
     resources = _resources()
     reg = resolve(resources, device_types=_DEVICE_TYPES)
+    assert reg is not None
     unbound = []
     discover(resources, reg.capabilities, reg.pattern_capabilities, log=unbound.append)
     assert unbound == []
diff --git a/tests/test_gas_cooktop_tp2x_ks_capabilities.py b/tests/test_gas_cooktop_tp2x_ks_capabilities.py
index 340675e..695f303 100644
--- a/tests/test_gas_cooktop_tp2x_ks_capabilities.py
+++ b/tests/test_gas_cooktop_tp2x_ks_capabilities.py
@@ -19,6 +19,7 @@ from tests.conftest import _load_device
 def _bound():
     resources = _load_device("gas_cooktop_tp2x_ks")
     reg = resolve(resources)
+    assert reg is not None
     return discover(resources, reg.capabilities, reg.pattern_capabilities), resources
 
 
@@ -31,6 +32,7 @@ def test_resolves_to_gas_cooktop_registry():
 def test_no_unbound_hrefs():
     _, resources = _bound()
     reg = resolve(resources)
+    assert reg is not None
     unbound = []
     discover(resources, reg.capabilities, reg.pattern_capabilities, log=unbound.append)
     assert unbound == []
diff --git a/tests/test_oven_tp2x_ks_walloven_capabilities.py b/tests/test_oven_tp2x_ks_walloven_capabilities.py
index 016e363..62eecc4 100644
--- a/tests/test_oven_tp2x_ks_walloven_capabilities.py
+++ b/tests/test_oven_tp2x_ks_walloven_capabilities.py
@@ -20,6 +20,7 @@ _DEVICE_TYPES = ("oic.wk.d", "oic.d.oven")
 def _bound():
     resources = _load_device("oven_tp2x_ks_walloven")
     reg = resolve(resources, device_types=_DEVICE_TYPES)
+    assert reg is not None
     return discover(resources, reg.capabilities, reg.pattern_capabilities), resources
 
 
@@ -31,6 +32,7 @@ def test_oic_device_type_resolves_to_oven_registry():
 def test_no_unbound_hrefs():
     resources = _load_device("oven_tp2x_ks_walloven")
     reg = resolve(resources, device_types=_DEVICE_TYPES)
+    assert reg is not None
     unbound = []
     discover(resources, reg.capabilities, reg.pattern_capabilities, log=unbound.append)
     assert unbound == []
diff --git a/tests/test_refrigerator_tp1x_ref_21k_airfilter_capabilities.py b/tests/test_refrigerator_tp1x_ref_21k_airfilter_capabilities.py
index 4a05fe2..cf5867e 100644
--- a/tests/test_refrigerator_tp1x_ref_21k_airfilter_capabilities.py
+++ b/tests/test_refrigerator_tp1x_ref_21k_airfilter_capabilities.py
@@ -15,6 +15,7 @@ from tests.conftest import _load_device
 def _bound():
     resources = _load_device("refrigerator_tp1x_ref_21k_airfilter")
     reg = resolve(resources)
+    assert reg is not None
     return discover(resources, reg.capabilities, reg.pattern_capabilities), resources
 
 
@@ -22,6 +23,7 @@ def test_no_unbound_hrefs():
     _, resources = _bound()
     unbound = []
     reg = resolve(resources)
+    assert reg is not None
     discover(resources, reg.capabilities, reg.pattern_capabilities, log=unbound.append)
     assert unbound == []