Failing test: http://w3c-test.org/url/urlsearchparams-delete.any.html
var url = new URL('http://example.com/?');
assert_equals(url.href, 'http://example.com/', 'url.href does not have ?');
assert_equals(url.search, '', 'url.search does not have ?');
}, 'Removing non-existent param removes ? from URL');
This is the only failing test for URLSearchParams.
Note that this bug also affects Safari on latest iOS.