Improve deprecation message for class-scoped fixtures as instance methods

src/_pytest/deprecated.py

@@ -34,12 +34,13 @@
     "Use @pytest.fixture instead; they are the same."
 )
 
-CLASS_FIXTURE_INSTANCE_METHOD = PytestRemovedIn10Warning(
-    "Class-scoped fixture defined as instance method is deprecated.\n"
-    "Instance attributes set in this fixture will NOT be visible to test methods,\n"
+CLASS_FIXTURE_INSTANCE_METHOD = UnformattedWarning(
+    PytestRemovedIn10Warning,
+    "Class-scoped fixtures defined as instance methods are deprecated.\n"
+    "Instance attributes set in the {fixturename!r} fixture will NOT be visible to test methods,\n"
     "as each test gets a new instance while the fixture runs only once per class.\n"
-    "Use @classmethod decorator and set attributes on cls instead.\n"
-    "See https://docs.pytest.org/en/stable/deprecations.html#class-scoped-fixture-as-instance-method"
+    "Use a @classmethod decorator below @pytest.fixture and set attributes on cls instead.\n"
+    "See https://docs.pytest.org/en/stable/deprecations.html#class-scoped-fixture-as-instance-method",
 )
 
 # This deprecation is never really meant to be removed.

src/_pytest/fixtures.py

@@ -1274,6 +1274,10 @@ def resolve_fixture_function(
 ) -> _FixtureFunc[FixtureValue]:
     """Get the actual callable that can be called to obtain the fixture
     value."""
+
+    def __tracebackhide__(e):
+        return issubclass(e.type, CLASS_FIXTURE_INSTANCE_METHOD.category)
+
     fixturefunc = fixturedef.func
     # The fixture function needs to be bound to the actual
     # request.instance so that code working with "fixturedef" behaves
@@ -1287,7 +1291,12 @@ def resolve_fixture_function(
             # classmethod: bound_to is the class itself (a type)
             # instance method: bound_to is an instance (not a type)
             if not isinstance(bound_to, type):
-                warnings.warn(CLASS_FIXTURE_INSTANCE_METHOD, stacklevel=2)
+                warnings.warn(
+                    CLASS_FIXTURE_INSTANCE_METHOD.format(
+                        fixturename=request.fixturename
+                    ),
+                    stacklevel=2,
+                )
 
     if instance is not None:
         # Handle the case where fixture is defined not in a test class, but some other class

testing/deprecated_test.py

@@ -104,7 +104,9 @@ def test_foo(self, fix):
     result = pytester.runpytest("-Werror::pytest.PytestRemovedIn10Warning")
     result.assert_outcomes(errors=1)
     result.stdout.fnmatch_lines(
-        ["*PytestRemovedIn10Warning: Class-scoped fixture defined as instance method*"]
+        [
+            "*PytestRemovedIn10Warning: Class-scoped fixtures defined as instance methods*"
+        ]
     )