I'd like to see the first set of tests in `test_set_slice` use a loop for more clarity; e.g.
``` python
left_slices = [slice(None), 1, slice(None)]
right_slices = [0, slice(None), slice(None)]
values = [1, 2, 3]
for (ls, rs, v) in zip(left_slices, right_slices, values):
    A[ls, rs] = v
    B[ls, rs] = v
    assert_array_equal(A.toarray(), B)
```