def test_add_revision_one_head(self):
        map_ = RevisionMap(lambda: [
            Revision('a', ()),
            Revision('b', ('a', )),
            Revision('c', ('b', )),
        ])
        eq_(map_.heads, ('c', ))

        map_.add_revision(Revision('d', ('c', )))
        eq_(map_.heads, ('d', ))
    def test_add_revision_two_head(self):
        map_ = RevisionMap(lambda: [
            Revision('a', ()),
            Revision('b', ('a', )),
            Revision('c1', ('b', )),
            Revision('c2', ('b', )),
        ])
        eq_(map_.heads, ('c1', 'c2'))

        map_.add_revision(Revision('d1', ('c1', )))
        eq_(map_.heads, ('c2', 'd1'))