human
Solve the following python programming problem given the following code:
# %load test_stack.py
from nose.tools import assert_equal

class TestStack(object):

    # TODO: It would be better if we had unit tests for each
    # method in addition to the following end-to-end test
    def test_end_to_end(self):
        print('Test: Empty stack')
        stack = Stack()
        assert_equal(stack.peek(), None)
        assert_equal(stack.pop(), None)

        print('Test: One element')
        top = Node(5)
        stack = Stack(top)
        assert_equal(stack.pop(), 5)
        assert_equal(stack.peek(), None)

        print('Test: More than one element')
        stack = Stack()
        stack.push(1)
        stack.push(2)
        stack.push(3)
        assert_equal(stack.pop(), 3)
        assert_equal(stack.peek(), 2)
        assert_equal(stack.pop(), 2)
        assert_equal(stack.peek(), 1)
        assert_equal(stack.is_empty(), False)
        assert_equal(stack.pop(), 1)
        assert_equal(stack.peek(), None)
        assert_equal(stack.is_empty(), True)

        print('Success: test_end_to_end')

def main():
    test = TestStack()
    test.test_end_to_end()

if __name__ == '__main__':
    main()
Given the above code, generate some markdown instructions for it.
assistant
#Here is the Python code you requested.

Unit Test
The following unit test is expected to fail until you solve the challenge.