def test_grain_statistics(self):
datapts = [(4, 100), (2, 99), (1, 97), (0.5, 83.4),
(0.25, 42), (0.125, 10), (0.062, 3.2), (0.031, 2)]
f = GSD_calculator(datapts = datapts)
f.run()
grain_stats = f.characteristic_size([70,50,30])
self.assertEqual(grain_stats[0], 0.39951691807960471)
self.assertEqual(grain_stats[1], 0.28583147875448067)
self.assertEqual(grain_stats[2], 0.19277635317599259)
