bpo-32255: Add tests for csv.writer

Author: Licht-T

Lib/test/test_csv.py

@@ -211,6 +211,25 @@ def write(self, buf):
             fileobj.seek(0)
             self.assertEqual(fileobj.read(), "a,b\r\nc,d\r\n")
 
+    def test_writerows_with_none(self):
+        with TemporaryFile("w+", newline='') as fileobj:
+            writer = csv.writer(fileobj)
+            writer.writerows([['a',None],[None,'d']])
+            fileobj.seek(0)
+            self.assertEqual(fileobj.read(), "a,\r\n,d\r\n")
+
+        with TemporaryFile("w+", newline='') as fileobj:
+            writer = csv.writer(fileobj)
+            writer.writerows([[None],['a']])
+            fileobj.seek(0)
+            self.assertEqual(fileobj.read(), '""\r\na\r\n')
+
+        with TemporaryFile("w+", newline='') as fileobj:
+            writer = csv.writer(fileobj)
+            writer.writerows([['a'],[None]])
+            fileobj.seek(0)
+            self.assertEqual(fileobj.read(), 'a\r\n""\r\n')
+
     @support.cpython_only
     def test_writerows_legacy_strings(self):
         import _testcapi