import unittest

from benedict.core import swap as _swap


class swap_test_case(unittest.TestCase):
    """
    This class describes a swap test case.
    """

    def test_swap(self):
        d = {
            "a": 1,
            "b": 2,
            "c": 3,
        }
        _swap(d, "a", "b")
        r = {
            "a": 2,
            "b": 1,
            "c": 3,
        }
        self.assertEqual(d, r)

    def test_swap_with_same_key(self):
        d = {
            "a": 1,
            "b": 2,
        }
        _swap(d, "a", "a")
        r = {
            "a": 1,
            "b": 2,
        }
        self.assertEqual(d, r)

    def test_swap_with_invalid_key(self):
        d = {
            "a": 1,
            "b": 2,
            "c": 3,
        }
        with self.assertRaises(KeyError):
            _swap(d, "a", "d")