tests/test_cadenus.py

   1 import pytest
   2 import string
   3
   4 from szyfrow.cadenus import *
   5 from szyfrow.support.utilities import *
   6
   7 def test_keycolumn():
   8     assert make_cadenus_keycolumn()['a'] == 0
   9     assert make_cadenus_keycolumn()['b'] == 1
  10     assert make_cadenus_keycolumn()['c'] == 2
  11     assert make_cadenus_keycolumn()['v'] == 21
  12     assert make_cadenus_keycolumn()['w'] == 21
  13     assert make_cadenus_keycolumn()['z'] == 24
  14     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  15         reverse=True)['a'] == 1
  16     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  17         reverse=True)['b'] == 0
  18     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  19         reverse=True)['c'] == 24
  20     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  21         reverse=True)['i'] == 18
  22     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  23         reverse=True)['j'] == 18
  24     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  25         reverse=True)['v'] == 6
  26     assert make_cadenus_keycolumn(doubled_letters='ij', start='b',
  27         reverse=True)['z'] == 2
  28
  29
  30 def test_encipher_message():
  31     plaintext = sanitise('''Whoever has made a voyage up the Hudson must
  32         remember the Kaatskill mountains. They are a dismembered branch of
  33         the great''')
  34     keycol = make_cadenus_keycolumn(doubled_letters='vw', start='a', reverse=True)
  35     ciphertext = cadenus_encipher(plaintext, 'wink', keycol)
  36     expected = 'antodeleeeuhrsidrbhmhdrrhnimefmthgeaetakseomehetyaasuvoyegrastmmuuaeenabbtpchehtarorikswosmvaleatned'
  37     assert ciphertext == expected
  38
  39     plaintext = sanitise('''a severe limitation on the usefulness of the
  40         cadenus is that every message must be a multiple of twenty-five
  41         letters long''')
  42     ciphertext = cadenus_encipher(plaintext, 'easy', keycol)
  43     expected = 'systretomtattlusoatleeesfiyheasdfnmschbhneuvsnpmtofarenuseieeieltarlmentieetogevesitfaisltngeeuvowul'
  44     assert ciphertext == expected
  45
  46
  47 def test_decipher_message():
  48     plaintext = sanitise('''Whoever has made a voyage up the Hudson must
  49         remember the Kaatskill mountains. They are a dismembered branch of
  50         the great''')
  51     keycol = make_cadenus_keycolumn(doubled_letters='vw', start='a', reverse=True)
  52     for key in ['wink', 'easy']:
  53         enciphered = cadenus_encipher(plaintext, key, keycol)
  54         deciphered = cadenus_decipher(enciphered, key, keycol)
  55         assert deciphered == plaintext
  56
  57
  58 def test_cadenus_break():
  59     plaintext = sanitise('''You will rejoice to hear that no disaster has accompanied the
  60 commencement of an enterprise which you have regarded with such evil
  61 forebodings.  I arrived here yesterday, and my first task is to assure
  62 my dear sister of my welfare and increasing confidence in the success
  63 of my undertaking.
  64
  65 I am already far north of London, and as I walk in the streets of
  66 Petersburgh, I feel a cold northern breeze play upon my cheeks, which
  67 braces my nerves and fills me with delight.  Do you understand this
  68 feeling?  This breeze, which has travelled from the regions towards
  69 which I am advancing, gives me a foretaste of those icy climes.
  70 Inspirited by this wind of promise, my daydreams become more fervent
  71 and vivid.
  72
  73 I try in vain to be persuaded that the pole is the seat of
  74 frost and desolation; it ever presents itself to my imagination as the
  75 region of beauty and delight.  There, Margaret, the sun is for ever
  76 visible, its broad disk just skirting the horizon and diffusing a
  77 perpetual splendour.  There—for with your leave, my sister, I will put
  78 some trust in preceding navigators—there snow and frost are banished;
  79 and, sailing over a calm sea, we may be wafted to a land surpassing in
  80 wonders and in beauty every region hitherto discovered on the habitable
  81 globe.
  82
  83 Its productions and features may be without example, as the
  84 phenomena of the heavenly bodies undoubtedly are in those undiscovered
  85 solitudes.  What may not be expected in a country of eternal light?  I
  86 may there discover the wondrous power which attracts the needle and may
  87 regulate a thousand celestial observations that require only this
  88 voyage to render their seeming eccentricities consistent for ever.  I
  89 shall satiate my ardent curiosity with the sight of a part of the world
  90 never before visited, and may tread a land never before imprinted by
  91 the foot of man. These are my enticements, and they are sufficient to
  92 conquer all fear of danger or death and to induce me to commence this
  93 laborious voyage with the joy a child feels when he embarks in a little
  94 boat, with his holiday mates, on an expedition of discovery up his
  95 native river. '''
  96 )
  97     expected_key = 'swashbuckling'
  98     chunk_len = len(transpositions_of(expected_key)) * 25
  99     target = plaintext + pad(len(plaintext), chunk_len, 'a')
 100     expected_score = Ptrigrams(target)
 101     expected_keycol = make_cadenus_keycolumn(doubled_letters='vw', start='a',
 102         reverse=True)
 103
 104     ciphertext = cadenus_encipher(plaintext, expected_key, expected_keycol)
 105
 106     dictionary = ['clearinghouse', 'computerising', 'counterclaims',
 107         'housewarmings',  'intravenously', 'liquefactions', 'somersaulting',
 108         'sportsmanlike', 'swashbuckling']
 109
 110     # dictionary = ['swashbuckling']
 111
 112     (key, keycol), score = cadenus_break(ciphertext, wordlist=dictionary,
 113         fitness=Ptrigrams)
 114
 115     assert key == expected_key
 116     assert keycol == expected_keycol
 117     assert score == pytest.approx(expected_score)