Produce a warning when unknown arguments are passed to pytest.param()

src/_pytest/deprecated.py

@@ -93,3 +93,9 @@ PYTEST_WARNS_UNKNOWN_KWARGS = UnformattedWarning(
     "pytest.warns() got unexpected keyword arguments: {args!r}.\n"
     "This will be an error in future versions.",
 )
+
+PYTEST_PARAM_UNKNOWN_KWARGS = UnformattedWarning(
+    PytestDeprecationWarning,
+    "pytest.param() got unexpected keyword arguments: {args!r}.\n"
+    "This will be an error in future versions.",
+)

src/_pytest/mark/structures.py

@@ -10,6 +10,7 @@ from ..compat import ascii_escaped
 from ..compat import getfslineno
 from ..compat import MappingMixin
 from ..compat import NOTSET
+from _pytest.deprecated import PYTEST_PARAM_UNKNOWN_KWARGS
 from _pytest.outcomes import fail
 
 EMPTY_PARAMETERSET_OPTION = "empty_parameter_set_mark"
@@ -60,20 +61,25 @@ def get_empty_parameterset_mark(config, argnames, func):
 
 class ParameterSet(namedtuple("ParameterSet", "values, marks, id")):
     @classmethod
-    def param(cls, *values, **kw):
-        marks = kw.pop("marks", ())
+    def param(cls, *values, **kwargs):
+        marks = kwargs.pop("marks", ())
         if isinstance(marks, MarkDecorator):
             marks = (marks,)
         else:
             assert isinstance(marks, (tuple, list, set))
 
-        id_ = kw.pop("id", None)
+        id_ = kwargs.pop("id", None)
         if id_ is not None:
             if not isinstance(id_, six.string_types):
                 raise TypeError(
                     "Expected id to be a string, got {}: {!r}".format(type(id_), id_)
                 )
             id_ = ascii_escaped(id_)
+
+        if kwargs:
+            warnings.warn(
+                PYTEST_PARAM_UNKNOWN_KWARGS.format(args=sorted(kwargs)), stacklevel=3
+            )
         return cls(values, marks, id_)
 
     @classmethod

src/_pytest/outcomes.py

@@ -97,8 +97,7 @@ def skip(msg="", **kwargs):
     __tracebackhide__ = True
     allow_module_level = kwargs.pop("allow_module_level", False)
     if kwargs:
-        keys = [k for k in kwargs.keys()]
-        raise TypeError("unexpected keyword arguments: {}".format(keys))
+        raise TypeError("unexpected keyword arguments: {}".format(sorted(kwargs)))
     raise Skipped(msg=msg, allow_module_level=allow_module_level)
 
 

src/_pytest/python_api.py

@@ -682,7 +682,7 @@ def raises(expected_exception, *args, **kwargs):
             match_expr = kwargs.pop("match")
         if kwargs:
             msg = "Unexpected keyword arguments passed to pytest.raises: "
-            msg += ", ".join(kwargs.keys())
+            msg += ", ".join(sorted(kwargs))
             raise TypeError(msg)
         return RaisesContext(expected_exception, message, match_expr)
     elif isinstance(args[0], str):