'Test firwin2 when window=None.'

def test04(self):

    ntaps = 5
    freq = [0.0, 0.5, 0.5, 1.0]
    gain = [1.0, 1.0, 0.0, 0.0]
    taps = firwin2(ntaps, freq, gain, window=None, nfreqs=8193)
    alpha = (0.5 * (ntaps - 1))
    m = (np.arange(0, ntaps) - alpha)
    h = (0.5 * sinc((0.5 * m)))
    assert_array_almost_equal(h, taps)
