1 files changed, 22 insertions, 0 deletions
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index 001b640..36daa61 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -332,6 +332,23 @@ class _AssertWarnsContext(_AssertRaisesBaseContext):
             self._raiseFailure("{} not triggered".format(exc_name))
 
 
+class _AssertNotWarnsContext(_AssertWarnsContext):
+
+    def __exit__(self, exc_type, exc_value, tb):
+        self.warnings_manager.__exit__(exc_type, exc_value, tb)
+        if exc_type is not None:
+            # let unexpected exceptions pass through
+            return
+        try:
+            exc_name = self.expected.__name__
+        except AttributeError:
+            exc_name = str(self.expected)
+        for m in self.warnings:
+            w = m.message
+            if isinstance(w, self.expected):
+                self._raiseFailure(f"{exc_name} triggered")
+
+
 class _OrderedChainMap(collections.ChainMap):
     def __iter__(self):
         seen = set()
@@ -811,6 +828,11 @@ class TestCase(object):
         context = _AssertWarnsContext(expected_warning, self)
         return context.handle('assertWarns', args, kwargs)
 
+    def _assertNotWarns(self, expected_warning, *args, **kwargs):
+        """The opposite of assertWarns. Private due to low demand."""
+        context = _AssertNotWarnsContext(expected_warning, self)
+        return context.handle('_assertNotWarns', args, kwargs)
+
     def assertLogs(self, logger=None, level=None):
         """Fail unless a log message of level *level* or higher is emitted
         on *logger_name* or its children.  If omitted, *level* defaults to