webdriver: add test for ignored fields to Set Timeouts

WebDriver is meant to ignore unfamiliar fields in JSON Objects generally,
and whilst we are testing that an empty object, {}, does not mutate
the timeout duration values, we are not testing unknown field keys.

Differential Revision: https://phabricator.services.mozilla.com/D33489

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1556387
gecko-commit: 2cdb92042b95a477756d47994974d975ebfd820d
gecko-integration-branch: autoland
gecko-reviewers: webdriver-reviewers, whimboo
diff --git a/webdriver/tests/set_timeouts/set.py b/webdriver/tests/set_timeouts/set.py
index d563f5f..6620f4d 100644
--- a/webdriver/tests/set_timeouts/set.py
+++ b/webdriver/tests/set_timeouts/set.py
@@ -30,10 +30,11 @@
     assert_error(response, "invalid argument")
 
 
-def test_parameters_empty_no_change(session):
+@pytest.mark.parametrize("value", [{}, {"a": 42}])
+def test_parameters_unknown_fields(session, value):
     original = session.timeouts._get()
 
-    response = set_timeouts(session, {})
+    response = set_timeouts(session, value)
     assert_success(response)
 
     assert session.timeouts._get() == original