diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index f722d3c..ba1a947 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -84,6 +84,8 @@ def test_registry_group_by_directive(group_str, expected):
     hook_groups = HOOK_REGISTRY.group_by_directive(*args)
     actual = {type(hook) for hook in hook_groups['Transaction']}
     assert actual.issuperset(expected)
+    if len(expected) == 1:
+        assert not (TransactionError in actual and PostingError in actual)
 
 def test_registry_unknown_group_name():
     with pytest.raises(ValueError):