Add the simple substitution cipher.

test/cipher_analytical_machine/ciphers/simple_substitution_test.clj

@@ -0,0 +1,44 @@
+(ns cipher-analytical-machine.ciphers.simple-substitution
+  (:require
+   [clojure.test :refer :all]
+   [cipher-analytical-machine.ciphers.simple-substitution :refer :all]))
+
+(deftest find-value-in-table-test
+  (let [table {\a 1 \b 2 \c 3}
+        rtable {1 \a 2 \b 3 \c}]
+    (testing "If the symbol is in the table as a key, then the result won't nil."
+      (are [key expected]
+          (= expected (find-value-in-table key table))
+        \a 1
+        \d nil
+        1 nil
+        5 nil))
+
+    (testing "If the digit is in the reversed table as a key, then the result won't nil."
+      (are [key expected]
+          (= expected (find-value-in-table key rtable))
+        \a nil
+        \d nil
+        1 \a
+        5 nil))))
+
+(deftest encrypt-message-text
+  (let [symbols "abc"
+        table {\a 1 \b 2 \c 3}]
+    (testing "The function must encrypt the message and remove unknown symbols."
+      (are [message key expected]
+          (= expected (encrypt-message message key table symbols))
+        "abc" 0 "1,2,3"
+        "abc" 1 "2,3,1"
+        "aDbdc" 0 "1,2,3"))))
+
+(deftest decrypt-message-text
+  (let [symbols "abc"
+        table {\a 1 \b 2 \c 3}]
+    (testing "The function must decrypt the message and remove unknown numbers."
+      (are [message key expected]
+          (= expected (decrypt-message message key table symbols))
+        "1,2,3" 0 "abc"
+        "2,3,1" 1 "abc"
+        "1,12,2,3" 0 "abc"))))
+