Add missing coverage for __set_name__

propcache/_helpers_c.pyx

@@ -73,7 +73,7 @@ cdef class cached_property:
         if self.name is None:
             raise TypeError(
                 "Cannot use cached_property instance"
-                "without calling __set_name__ on it.")
+                " without calling __set_name__ on it.")
         cdef dict cache = inst.__dict__
         val = cache.get(self.name, _sentinel)
         if val is _sentinel:

tests/test_cached_property.py

@@ -102,3 +102,45 @@ class TestPyCachedProperty(CachedPropertyMixin):
 
     class TestCCachedProperty(CachedPropertyMixin):
         cached_property = _helpers.cached_property_c  # type: ignore[assignment, attr-defined, unused-ignore] # noqa: E501
+
+
+def test_set_name():
+    """Test that the __set_name__ method is called and checked."""
+
+    class A:
+        def __init__(self):
+            self._cache = {}
+
+        @cached_property
+        def prop(self):
+            """Docstring."""
+            return 1
+
+    A.prop.__set_name__(A, "prop")
+
+    with pytest.raises(
+        TypeError,
+        match=(
+            r"Cannot assign the same cached_property to two "
+            r"different names \('prop' and 'something_else'\)."
+        ),
+    ):
+        A.prop.__set_name__(A, "something_else")
+
+
+def test_get_without_set_name():
+    """Test that get without __set_name__ fails."""
+    cp = cached_property(lambda s: None)
+
+    class A:
+        """A class."""
+
+    A.cp = cp
+    with pytest.raises(
+        TypeError,
+        match=(
+            r"Cannot use cached_property instance "
+            r"without calling __set_name__ on it."
+        ),
+    ):
+        _ = A().cp