def test_gridpoint2index(self):
"""
Should convert between 1D and 3D grid indices.
"""
vm = VM()
# should return an integer index
i0 = (10, 0, 3)
idx = vm.gridpoint2index(*i0)
self.assertEqual(type(idx), int)
# should return original 3D indices
i1 = vm.index2gridpoint(idx)
self.assertEqual(type(i1), tuple)
for j in range(3):
self.assertEqual(i0[j], i1[j])
