def test_alternation_ab(a, b):
    altAB = (a | b)
    assert (not altAB.accepts(''))
    assert altAB.accepts('a')
    assert altAB.accepts('b')
    assert (not altAB.accepts('aa'))
    assert (not altAB.accepts('ab'))
    assert (not altAB.accepts('ba'))
    assert (not altAB.accepts('bb'))
def test_alternation_ab(a, b):
    altAB = (a | b)
    assert (not altAB.accepts())
    assert altAB.accepts('a')
    assert altAB.accepts('b')
    assert (not altAB.accepts('aa'))
    assert (not altAB.accepts('ab'))
    assert (not altAB.accepts('ba'))
    assert (not altAB.accepts('bb'))