Add TypeError for bare @requires_crt usage and regression tests (#4734)

* Add TypeError for bare @requires_crt usage and regression tests

* use `is False` for consistency with `is True` assertion in requires_crt regression tests

Author: Alan4506

tests/__init__.py

@@ -52,6 +52,10 @@ def tearDown(self):
 
 
 def requires_crt(reason=None):
+    if callable(reason):
+        raise TypeError(
+            "Use @requires_crt() with parentheses, not bare @requires_crt"
+        )
     if reason is None:
         reason = "Test requires awscrt to be installed"
 

tests/unit/test_crt.py

@@ -231,3 +231,30 @@ def test_config_without_crt_support_emits_warning(
                 for r in caplog.records
             ]
         )
+
+
+class TestRequiresCrt:
+    def test_bare_requires_crt_fails_immediately(self):
+        with pytest.raises(TypeError):
+
+            @requires_crt
+            def my_test():
+                pass
+
+    def test_requires_crt_skips_when_no_crt(self):
+        with mock.patch('tests.HAS_CRT', False):
+
+            @requires_crt()
+            def my_test():
+                assert False
+
+            assert getattr(my_test, '__unittest_skip__', False) is True
+
+    def test_requires_crt_runs_when_crt_available(self):
+        with mock.patch('tests.HAS_CRT', True):
+
+            @requires_crt()
+            def my_test():
+                pass
+
+            assert getattr(my_test, '__unittest_skip__', False) is False