Add xfail marking support to backend test runner (#3542)

Signed-off-by: twata <twata@preferred.jp>

Co-authored-by: Ashwini Khade <askhade@microsoft.com>

onnx/backend/test/runner/__init__.py

@@ -58,6 +58,7 @@ def __init__(self, backend, parent_module=None):  # type: (Type[Backend], Option
         self._parent_module = parent_module
         self._include_patterns = set()  # type: Set[Pattern[Text]]
         self._exclude_patterns = set()  # type: Set[Pattern[Text]]
+        self._xfail_patterns = set()    # type: Set[Pattern[Text]]
 
         # This is the source of the truth of all test functions.
         # Properties `test_cases`, `test_suite` and `tests` will be
@@ -94,6 +95,10 @@ def exclude(self, pattern):  # type: (Text) -> Runner
         self._exclude_patterns.add(re.compile(pattern))
         return self
 
+    def xfail(self, pattern):  # type: (Text) -> Runner
+        self._xfail_patterns.add(re.compile(pattern))
+        return self
+
     def enable_report(self):  # type: () -> Runner
         import pytest  # type: ignore
 
@@ -120,6 +125,9 @@ def _filtered_test_items(self):  # type: () -> Dict[Text, Dict[Text, TestItem]]
                             'matched exclude pattern "{}"'.format(
                                 exclude.pattern)
                         )(item.func)
+                for xfail in self._xfail_patterns:
+                    if xfail.search(name):
+                        item.func = unittest.expectedFailure(item.func)
                 filtered[category][name] = item
         return filtered