'Test the Progress.add_counts() method'

def test_add(self):

    prg1 = Progress(0, 2)
    prg2 = Progress(1, 3)
    prg3 = Progress(2, 5)
    prg_none = None
    add = (lambda a, b: Progress.add_counts(a, b).frac())
    self.assertEqual(add(prg1, prg1), (0, 4))
    self.assertEqual(add(prg1, prg2), (1, 5))
    self.assertEqual(add(prg2, prg3), (3, 8))
    self.assertEqual(add(prg2, prg_none), prg2.frac())
    self.assertEqual(add(prg_none, prg2), prg2.frac())
