'Tests for Gregorian Date to/from Julian Day conversion'

def testGregorianJDConversion(self):

    test_dates = ((1973, 4, 21, 2441793.5), (1345, 5, 13, 2212443.5), (2017, 11, 8, 2458065.5))
    c = S3Calendar()
    gregorian_to_jd = c._gregorian_to_jd
    jd_to_gregorian = c._jd_to_gregorian
    assertEqual = self.assertEqual
    for (year, month, day, jd) in test_dates:
        assertEqual(gregorian_to_jd(year, month, day), jd)
        assertEqual(jd_to_gregorian(jd), (year, month, day))
