stack_test.py

#!python

from stack import Stack
import unittest


class StackTest(unittest.TestCase):

    def test_init(self):
        s = Stack()
        assert s.peek() is None
        assert s.length() == 0
        assert s.is_empty() is True

    def test_init_with_list(self):
        s = Stack(['A', 'B', 'C'])
        assert s.peek() == 'C'
        assert s.length() == 3
        assert s.is_empty() is False

    def test_length(self):
        s = Stack()
        assert s.length() == 0
        s.push('A')
        assert s.length() == 1
        s.push('B')
        assert s.length() == 2
        s.pop()
        assert s.length() == 1
        s.pop()
        assert s.length() == 0

    def test_push(self):
        s = Stack()
        s.push('A')
        assert s.peek() == 'A'
        assert s.length() == 1
        s.push('B')
        assert s.peek() == 'B'
        assert s.length() == 2
        s.push('C')
        assert s.peek() == 'C'
        assert s.length() == 3
        assert s.is_empty() is False

    def test_peek(self):
        s = Stack()
        assert s.peek() is None
        s.push('A')
        assert s.peek() == 'A'
        s.push('B')
        assert s.peek() == 'B'
        s.pop()
        assert s.peek() == 'A'
        s.pop()
        assert s.peek() is None

    def test_pop(self):
        s = Stack(['A', 'B', 'C'])
        assert s.pop() == 'C'
        assert s.length() == 2
        assert s.pop() == 'B'
        assert s.length() == 1
        assert s.pop() == 'A'
        assert s.length() == 0
        assert s.is_empty() is True
        with self.assertRaises(ValueError):
            s.pop()


if __name__ == '__main__':
    unittest.main()