def test_LUdecomp():
testmat = DenseMatrix([[0, 2, 5, 3], [3, 3, 7, 4], [8, 4, 0, 2],
[-2, 6, 3, 4]])
L, U, p = testmat.LUdecomposition()
res = L * U
for orig, new in p:
res.row_swap(orig, new)
assert res - testmat == zeros(4)
