How could the player possibly move up? Python Testing

I think this is an instance where "[doctest] uses a shallow copy of [a module] M‘s globals" Here's a failing doc-test demonstrating

SOME_CONSTANT = True

def test_constant_setting():
    """

    >>> SOME_CONSTANT = False
    >>> test_constant_setting()
    False

    """
    return SOME_CONSTANT

• And execution in the repl

>>> SOME_CONSTANT
True
>>> test_constant_setting()
True
>>> SOME_CONSTANT = False
>>> SOME_CONSTANT
False
>>> test_constant_setting()
True

Wrapping the constant in a class allows it to be set in the test but then it's no longer a constant and will effect the running of other tests that reference it. Wrapping the whole in a Game class and setting it's dimensions in build_cell seems a decent start.

A test in this case might look something like

def get_moves(player):
    """Based on the tuple of the player's position, return the list of acceptable moves

    >>> cells = build_cells(2, 2)
    >>> get_moves((0, 0))
    ['RIGHT', 'DOWN']
    >>> get_moves((1, 1))
    ['LEFT', 'UP']

    """

Unfortunately that introduces classes which increases the complexity of the lesson.

Because the get_moves function uses the equality operator to check for specific board positions rather than an actual boundary, and there is no code that prevents using the get moves function in isolation with an illegal board position, the get_moves function returns an output that doesn't make sense given an illegal board position. Of course, provided the player starts on the board, which they always will when running the actual game, the get_moves function always works properly.