exercism/elixir/simple-cipher/test/simple_cipher_test.exs

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2024-08-22 00:23:30 +00:00
defmodule SimpleCipherTest do
use ExUnit.Case
test "encoding with 'a' returns the original text" do
assert SimpleCipher.encode("a", "a") == "a"
assert SimpleCipher.encode("b", "a") == "b"
assert SimpleCipher.encode("c", "a") == "c"
end
test "encoding with another key returns shifted text" do
assert SimpleCipher.encode("a", "d") == "d"
assert SimpleCipher.encode("b", "d") == "e"
assert SimpleCipher.encode("c", "d") == "f"
end
test "decoding with 'a' returns the original text" do
assert SimpleCipher.decode("a", "a") == "a"
assert SimpleCipher.decode("b", "a") == "b"
assert SimpleCipher.decode("c", "a") == "c"
end
test "decoding with another key returns unshifted text" do
assert SimpleCipher.decode("d", "d") == "a"
assert SimpleCipher.decode("e", "d") == "b"
assert SimpleCipher.decode("f", "d") == "c"
end
test "key uses per-letter translation for encoding" do
key = "abc"
assert SimpleCipher.encode("abc", key) == "ace"
assert SimpleCipher.encode("bcd", key) == "bdf"
assert SimpleCipher.encode("cde", key) == "ceg"
assert SimpleCipher.encode("aaaaaaaaaa", "abcdefghij") == "abcdefghij"
end
test "key uses per-letter translation for decoding" do
key = "abc"
assert SimpleCipher.decode("ace", key) == "abc"
assert SimpleCipher.decode("bdf", key) == "bcd"
assert SimpleCipher.decode("ceg", key) == "cde"
assert SimpleCipher.decode("abcdefghij", "abcdefghij") == "aaaaaaaaaa"
end
test "reversible" do
key = "abcdefghij"
plaintext = "abcdefghij"
assert plaintext |> SimpleCipher.encode(key) |> SimpleCipher.decode(key) == plaintext
end
test "can double shift encode" do
assert SimpleCipher.encode("iamapandabear", "iamapandabear") == "qayaeaagaciai"
end
test "can wrap on encode" do
assert SimpleCipher.encode("zzzzzzzzzz", "abcdefghij") == "zabcdefghi"
end
test "can wrap on decode" do
assert SimpleCipher.decode("zabcdefghi", "abcdefghij") == "zzzzzzzzzz"
end
test "can encode messages longer than the key" do
assert SimpleCipher.encode("abc", "a") == "abc"
assert SimpleCipher.encode("abcdefghi", "abc") == "acedfhgik"
assert SimpleCipher.encode("iamapandabear", "abc") == "iboaqcnecbfcr"
end
test "can decode messages longer than the key" do
assert SimpleCipher.decode("abc", "a") == "abc"
assert SimpleCipher.decode("acedfhgik", "abc") == "abcdefghi"
assert SimpleCipher.decode("iboaqcnecbfcr", "abc") == "iamapandabear"
end
test "if key is longer than text, only use as much as needed" do
key = "somewhatlongkey"
assert SimpleCipher.encode("abc", key) == "spo"
assert SimpleCipher.decode("abc", key) == "inq"
end
test "if you know both the encoded and decoded text, you can figure out the key" do
key = "supersecretkey"
plaintext = "attackxatxdawn"
ciphertext = SimpleCipher.encode(plaintext, key)
assert SimpleCipher.decode(ciphertext, plaintext) == key
end
test "can generate keys of given length" do
assert String.length(SimpleCipher.generate_key(16)) == 16
assert String.length(SimpleCipher.generate_key(128)) == 128
assert String.length(SimpleCipher.generate_key(256)) == 256
end
test "generated keys are random" do
keys = Enum.map(0..100, fn _ -> SimpleCipher.generate_key(16) end)
assert keys == Enum.uniq(keys)
end
test "generated keys contain lowercase letters only" do
keys = Enum.map(0..100, fn _ -> SimpleCipher.generate_key(16) end)
assert Enum.all?(keys, &(&1 =~ ~r/^[a-z]*$/))
end
test "generated keys can be used to encode and decode text" do
Enum.each(0..100, fn _ ->
key = SimpleCipher.generate_key(16)
plaintext = "iamapandabear"
assert plaintext |> SimpleCipher.encode(key) |> SimpleCipher.decode(key) == plaintext
end)
end
end