old_contents: 
  
  import numpy as np
  import pytest
  
  from landlab import RasterModelGrid, CORE_NODE
  
  
  # test all grid elements
  
  
  # test bad grid elements
  
  
  # where is size of elements
  # where is list of types
  # where is list but use patches (raises value error)
  #
  
  # vertical plane
  
  # x and y of multiple types of grid elements
  # ask for a plane of something without X and y.
  
  # test bad distribution name.
  
new_contents: 
  
  import numpy as np
  from numpy.testing import assert_array_equal
  import pytest
  
  from landlab import RasterModelGrid, CORE_NODE, CLOSED_NODE
  from landlab.values import random, plane, constant, sine
  from landlab.values.synthetic import _plane_function
  
  _NORMAL = (1, 1, 1)
  _POINT = (0, 0, 0)
  
  
  def test_bad_grid_element_name():
      mg = RasterModelGrid((4, 4))
      with pytest.raises(KeyError):
          constant(mg, 'some_flux', 'not_a_grid_element', constant=1.0)
  
  
  def test_bad_distribution_name():
      mg = RasterModelGrid((4, 4))
      with pytest.raises(ValueError):
          random(mg, 'values', 'node', distribution='not_a_distribution')
  
  
  def test_vertical_plane():
      mg = RasterModelGrid((4, 4))
      with pytest.raises(ValueError):
          plane(mg, 'values', normal=(0., 1., 0.))
  
  
  def test_no_xy_values():
      mg = RasterModelGrid((4, 4))
      with pytest.raises(ValueError):
          plane(mg, 'values', "patch")
  
  
  def test_xy_node():
      mg = RasterModelGrid((4, 4))
      vals = plane(mg, 'values', "node", normal=_NORMAL)
      truth = _plane_function(mg.x_of_node, mg.y_of_node,
                              point=_POINT,
                              normal=_NORMAL)
      assert_array_equal(vals, truth)
  
  
  def test_xy_cell():
      mg = RasterModelGrid((4, 4))
      vals = plane(mg, 'values', "cell", normal=_NORMAL)
      truth = _plane_function(mg.x_of_cell, mg.y_of_cell,
                              point=_POINT,
                              normal=_NORMAL)
      assert_array_equal(vals, truth)
  
  
  def test_xy_link():
      mg = RasterModelGrid((4, 4))
      vals = plane(mg, 'values', "link", normal=_NORMAL)
      truth = _plane_function(mg.x_of_link, mg.y_of_link,
                              point=_POINT,
                              normal=_NORMAL)
      assert_array_equal(vals, truth)
  
  
  def test_xy_patch():
      mg = RasterModelGrid((4, 4))
      vals = plane(mg, 'values', "face", normal=_NORMAL)
      truth = _plane_function(mg.x_of_face, mg.y_of_face,
                              point=_POINT,
                              normal=_NORMAL)
      assert_array_equal(vals, truth)
  
  
  def test_where_status_with_patches():
      mg = RasterModelGrid((4, 4))
      with pytest.raises(ValueError):
          constant(mg, 'values', "patch", where=CORE_NODE)
  
  
  def test_multiple_status_node():
      mg = RasterModelGrid((4, 4))
      mg.se
  
  # test all grid elements
  
  
  # where is size of elements
  # where is list of types
  # where is list but use patches (raises value error)
  
  
  # x and y of multiple types of grid elements
  # ask for a plane of something without X and y.
  
subject: test wip