Code review comment for lp:~rvb/maas/bug-1413030

+ self.assertEqual(
+ ['hidden', 'hidden'],
+ [os_system_class, distro_series_class])

Do this in two assertions, something like:

        os_system_class = add_node_snippet.cssselect(
            "[for=id_osystem]")[0].attrib['class']
        self.expectThat(os_system_class, Equals('hidden'))

        distro_series_class = add_node_snippet.cssselect(
            "[for=id_distro_series]")[0].attrib['class']
        self.expectThat(distro_series_class, Equals('hidden'))

Better still, express what you're trying to test:

        get_class = lambda node: node.attrib['class']
        node_is_hidden = AfterPreprocessing(get_class, Equals('hidden'))

        self.expectThat(
            add_node_snippet.cssselect("[for=id_osystem]")[0],
            node_is_hidden)
        self.expectThat(
            add_node_snippet.cssselect("[for=id_distro_series]")[0],
            node_is_hidden)

Or even:

        self.expectThat(
            add_node_snippet.cssselect(".hidden [for=id_osystem]"),
            Not(HasLength(0)))
        self.expectThat(
            add_node_snippet.cssselect(".hidden [for=id_distro_series]"),
            Not(HasLength(0)))