def test_matrix_is_valid():
fn = odl.rn(5)
sparse_mat = _sparse_matrix(fn)
dense_mat = _dense_matrix(fn)
bad_mat = np.eye(5)
bad_mat[0, 0] = 0
w_sparse = NumpyFnMatrixWeighting(sparse_mat)
w_dense = NumpyFnMatrixWeighting(dense_mat)
w_bad = NumpyFnMatrixWeighting(bad_mat)
with pytest.raises(NotImplementedError):
w_sparse.is_valid()
assert w_dense.is_valid()
assert not w_bad.is_valid()
