'Check time arithmetic as well as properly keeping track of whether
a time is a scalar or a vector'

def test_sub_vector(self):

    t = Time(0.0, format='mjd', scale='utc')
    t2 = Time([0.0, 1.0], format='mjd', scale='utc')
    dt = TimeDelta(100.0, format='jd')
    dt2 = TimeDelta([100.0, 200.0], format='jd')
    out = (t - dt)
    assert allclose_jd(out.mjd, (-100.0))
    assert out.isscalar
    out = (t - dt2)
    assert allclose_jd(out.mjd, [(-100.0), (-200.0)])
    assert (not out.isscalar)
    out = (t2 - dt)
    assert allclose_jd(out.mjd, [(-100.0), (-99.0)])
    assert (not out.isscalar)
    out = (dt - dt)
    assert allclose_jd(out.jd, 0.0)
    assert out.isscalar
    out = (dt - dt2)
    assert allclose_jd(out.jd, [0.0, (-100.0)])
    assert (not out.isscalar)
