def test_project_euler_big_number(self):
     series = (
         "731671765313306249192251196744265747423553491949349698352031277450632623957"
         "831801698480186947885184385861560789112949495459501737958331952853208805511"
         "125406987471585238630507156932909632952274430435576689664895044524452316173"
         "185640309871112172238311362229893423380308135336276614282806444486645238749"
         "303589072962904915604407723907138105158593079608667017242712188399879790879"
         "227492190169972088809377665727333001053367881220235421809751254540594752243"
         "525849077116705560136048395864467063244157221553975369781797784617406495514"
         "929086256932197846862248283972241375657056057490261407972968652414535100474"
         "821663704844031998900088952434506585412275886668811642717147992444292823086"
         "346567481391912316282458617866458359124566529476545682848912883142607690042"
         "242190226710556263211111093705442175069416589604080719840385096245544436298"
         "123098787992724428490918884580156166097919133875499200524063689912560717606"
         "058861164671094050775410022569831552000559357297257163626956188267042825248"
         "3600823257530420752963450"
     )
     self.assertEqual(23514624000, largest_product(series, 13))

 def test_tiny_number(self):
     self.assertEqual(9, largest_product("19", 2))

 def test_largest_product_of_2(self):
     self.assertEqual(72, largest_product("0123456789", 2))

 def test_nonzero_slice_size_and_empty_string(self):
     with self.assertRaises(ValueError):
         largest_product("", 1)

 def test_identity_with_nonempty_string(self):
     self.assertEqual(1, largest_product("123", 0))

 def test_string_where_all_spans_contain_zero(self):
     self.assertEqual(0, largest_product("99099", 3))

 def test__largest_product_span_equals_length(self):
     self.assertEqual(18, largest_product("29", 2))

 def test_identity(self):
     self.assertEqual(1, largest_product("", 0))

 def test_digits_with_invalid_character(self):
     with self.assertRaises(ValueError):
         largest_product("1234a5", 2)

 def test_span_long_than_number(self):
     with self.assertRaises(ValueError):
         largest_product("123", 4)

 def test_all_digits_zero(self):
     self.assertEqual(0, largest_product("0000", 2))

 def test_big_number(self):
     series = "73167176531330624919225119674426574742355349194934"
     self.assertEqual(23520, largest_product(series, 6))

 def test_largest_product_of_5(self):
     self.assertEqual(15120, largest_product("0123456789", 5))

 def test_largest_product_of_3(self):
     self.assertEqual(504, largest_product("0123456789", 3))

 def test_largest_product_of_3(self):
     self.assertEqual(270, largest_product("1027839564", 3))

 def test_negative_span(self):
     with self.assertRaises(ValueError):
         largest_product("12345", -1)

 def test_big_number(self):
     series = "52677741234314237566414902593461595376319419139427"
     self.assertEqual(28350, largest_product(series, 6))

 def test_string_with_all_zeroes(self):
     self.assertEqual(0, largest_product("0000", 2))

 def test_slices_bigger_than_number(self):
     with self.assertRaises(ValueError):
         largest_product("012", 4)

 def test_largest_product_of_2_unordered(self):
     self.assertEqual(48, largest_product("576802143", 2))