I think there are cases where we can't always override the xml, like if the test_timeout has been exceeded? As far as I can tell, Bazel will still output it's own xml.
(ii) I wouldn't be opposed to changing generate-xml.sh to insert a dummy classname attribute. But that wouldn't help the situation where a test runner produces a test.xml file that doesn't use the attribute.
@haxorz I think this is a good option. If there are test runners overriding the default xml file I would think the onus would be on the test runner to produce a valid result.