def METHOD_NAME(self):
    mass = 1.0
    cylinder = Cylinderd(1.0, 0.001)
    expectedVolume = (math.pi * math.pow(0.001, 2) * 1.0)
    self.assertEqual(expectedVolume, cylinder.volume())
    expectedDensity = mass / expectedVolume
    self.assertEqual(expectedDensity, cylinder.density_from_mass(mass))
    # Bad density
    cylinder2 = Cylinderd()
    self.assertGreater(0.0, cylinder2.density_from_mass(mass))