'Test extracting interface names from a stanza object.'

def testKeys(self):

    class TestStanza(ElementBase, ):
        name = 'foo'
        namespace = 'foo'
        interfaces = set(('bar', 'baz'))
        plugin_attrib = 'qux'
    register_stanza_plugin(TestStanza, TestStanza)
    stanza = TestStanza()
    self.failUnless((set(stanza.keys()) == set(('lang', 'bar', 'baz'))), 'Returned    set    of    interface    keys    does    not    match    expected.')
    stanza.enable('qux')
    self.failUnless((set(stanza.keys()) == set(('lang', 'bar', 'baz', 'qux'))), 'Incorrect    set    of    interface    and    plugin    keys.')
