Add a test for the 'orderby' task_list param

This is a simple parametrized test which ensures that `orderby` takes
and serializes strings and lists of strings correctly.

tests/functional/services/transfer/test_task_list.py

@@ -27,3 +27,26 @@ def test_task_list(client, client_kwargs, qs):
     # parsed_qs will have each value as a list (because query-params are a multidict)
     # so transform the test data to match before comparison
     assert parsed_qs == {k: [v] for k, v in qs.items()}
+
+
+@pytest.mark.parametrize(
+    "orderby_value, expected_orderby_param",
+    [
+        ("foo", "foo"),
+        (["foo"], "foo"),
+        ("foo,bar", "foo,bar"),
+        ("foo ASC,bar", "foo ASC,bar"),
+        (["foo ASC", "bar"], "foo ASC,bar"),
+        (["foo ASC", "bar DESC"], "foo ASC,bar DESC"),
+    ],
+)
+def test_task_list_orderby_parameter(client, orderby_value, expected_orderby_param):
+    load_response(client.task_list)
+    client.task_list(orderby=orderby_value)
+
+    req = get_last_request()
+    parsed_qs = urllib.parse.parse_qs(urllib.parse.urlparse(req.url).query)
+    assert "orderby" in parsed_qs
+    assert len(parsed_qs["orderby"]) == 1
+    orderby_param = parsed_qs["orderby"][0]
+    assert orderby_param == expected_orderby_param