PYTHON-3800 Add test for SRV URI with uppercase hostname (#1293)

(cherry picked from commit 1d7f2ea)

test/test_dns.py

@@ -21,7 +21,7 @@
 
 sys.path[0:0] = [""]
 
-from test import client_context, unittest
+from test import IntegrationTest, client_context, unittest
 from test.utils import wait_until
 
 from pymongo.common import validate_read_preference_tags
@@ -186,5 +186,13 @@ def test_invalid_host(self):
         )
 
 
+class TestCaseInsensitive(IntegrationTest):
+    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS tests require the dnspython module")
+    def test_connect_case_insensitive(self):
+        client = MongoClient("mongodb+srv://TEST1.TEST.BUILD.10GEN.cc/")
+        self.addCleanup(client.close)
+        self.assertGreater(len(client.topology_description.server_descriptions()), 1)
+
+
 if __name__ == "__main__":
     unittest.main()