def read(*parts):
    """
    Build an absolute path from *parts* and and return the contents of the
    resulting file.  Assume UTF-8 encoding.
    """
    with codecs.open(os.path.join(HERE, *parts), "rb", "utf-8") as f:
        return f.read()
def test_critical_angle():
    m1 = Medium('m1', n=1)
    m2 = Medium('m2', n=1.33)
    assert ae(critical_angle(m2, m1), 0.85, 2)