Enable check_untyped_defs mypy option for testing/ too

src/_pytest/_code/code.py

@@ -15,6 +15,7 @@ from typing import Dict
 from typing import Generic
 from typing import Iterable
 from typing import List
+from typing import Mapping
 from typing import Optional
 from typing import Pattern
 from typing import Sequence
@@ -728,7 +729,7 @@ class FormattedExcinfo:
                 failindent = indentstr
         return lines
 
-    def repr_locals(self, locals: Dict[str, object]) -> Optional["ReprLocals"]:
+    def repr_locals(self, locals: Mapping[str, object]) -> Optional["ReprLocals"]:
         if self.showlocals:
             lines = []
             keys = [loc for loc in locals if loc[0] != "@"]