def test_get_mass(self):
chunk = Chunk()
self.assertEquals(chunk.get_mass(), 0.0, "bad initial mass")
shard1 = Disc(gold, 5)
shard2 = Block(gold, self.unitsquare)
chunk.shards = [shard1, shard2]
self.assertEquals(chunk.get_mass(), (25 * pi + 1) * gold.density,
"bad mass")