def METHOD_NAME(self):
    n = 4
    points, simplices = example_simplex_mesh((n, n))
    mesh = discretize.SimplexMesh(points, simplices)
    G_sten = mesh.stencil_cell_gradient
    mod = np.zeros(mesh.n_cells)
    test_cell = 21
    mod[test_cell] = 1.0
    diff = G_sten @ mod
    np.testing.assert_equal(
        np.where(diff != 0.0)[0], np.sort(mesh._simplex_faces[21])
    )
    np.testing.assert_equal(diff[diff != 0.0], [-1, 1, -1])