Update luhn and add luhn test template

exercises/luhn/luhn.mustache

@@ -0,0 +1,9 @@
+(ns luhn-test
+  (:require [clojure.test :refer [deftest is testing]]
+            luhn))
+
+(deftest validity-tests
+{{#valid}}
+  (testing "{{{description}}}"
+    (is ({{{expected}}}? (luhn/valid? "{{{input}}}"))))
+{{/valid}})

exercises/luhn/src/example.clj

@@ -1,4 +1,5 @@
-(ns luhn)
+(ns luhn
+  (:require [clojure.string :as string]))
 
 (defn to-reversed-digits
   "returns a lazy sequence of least to most significant digits of n"
@@ -19,14 +20,15 @@
            (apply +))
       (mod 10)))
 
-(defn valid?
-  "whether n has a valid luhn check-digit"
+(defn string->long
+  "Strips any non-digit characters and converts the string into a Long"
   [n]
-  (zero? (checksum n)))
+  (-> n (string/replace #"[^0-9]+" "") Long/parseLong))
 
-(defn add-check-digit
-  "given a number, adds a luhn check digit at the end"
+(defn valid?
+  "whether n has a valid luhn check-digit"
   [n]
-  (let [n-shifted (* 10 n)
-        check-digit (- 10 (checksum n-shifted))]
-    (+ n-shifted check-digit)))
+  ; Numbers with non digit/whitespace or only 1 digit are invalid
+  (if (or (re-find #"[^0-9\s]+" n) (>= 1 (count (string/trim n))))
+    false
+    (zero? (-> n string->long checksum))))

exercises/luhn/test/luhn_test.clj

@@ -1,32 +1,32 @@
 (ns luhn-test
-  (:require [clojure.test :refer [deftest is]]
+  (:require [clojure.test :refer [deftest is testing]]
             luhn))
 
-(deftest checksum-works
-  (is (= 2 (luhn/checksum 10)))
-  (is (= 9 (luhn/checksum 90)))
-  (is (= 1 (luhn/checksum 100)))
-  (is (= 2 (luhn/checksum 1000)))
-  (is (= 1 (luhn/checksum 10000000000000000)))
-  (is (= 6 (luhn/checksum 1111)))
-  (is (= 0 (luhn/checksum 8763)))
-  (is (= 0 (luhn/checksum 2323200577663554))))
-
-(deftest valid?-works
-  (is (= true (luhn/valid? 18)))
-  (is (= true (luhn/valid? 59)))
-  (is (= false (luhn/valid? 63)))
-  (is (= true (luhn/valid? 8763)))
-  (is (= false (luhn/valid? 1111)))
-  (is (= true (luhn/valid? 4242424242424242)))
-  (is (= true (luhn/valid? 2323200577663554)))
-  (is (= false (luhn/valid? 2323200577663555)))
-  (is (= false (luhn/valid? 2223200577663554)))
-  (is (= false (luhn/valid? 3323200577663554))))
-
-(deftest add-check-digit-works
-  (is (= 18 (luhn/add-check-digit 1)))
-  (is (= 59 (luhn/add-check-digit 5)))
-  (is (= 8763 (luhn/add-check-digit 876)))
-  (is (= 4242424242424242 (luhn/add-check-digit 424242424242424)))
-  (is (= 2323200577663554 (luhn/add-check-digit 232320057766355))))
+(deftest validity-tests
+  (testing "single digit strings can not be valid"
+    (is (false? (luhn/valid? "1"))))
+  (testing "A single zero is invalid"
+    (is (false? (luhn/valid? "0"))))
+  (testing "simple valid sin"
+    (is (true? (luhn/valid? " 5 9 "))))
+  (testing "valid Canadian SIN"
+    (is (true? (luhn/valid? "046 454 286"))))
+  (testing "invalid Canadian SIN"
+    (is (false? (luhn/valid? "046 454 287"))))
+  (testing "invalid credit card"
+    (is (false? (luhn/valid? "8273 1232 7352 0569"))))
+  (testing "valid strings with a non-digit added become invalid"
+    (is (false? (luhn/valid? "046a 454 286"))))
+  (testing "punctuation is not allowed"
+    (is (false? (luhn/valid? "055-444-285"))))
+  (testing "symbols are not allowed"
+    (is (false? (luhn/valid? "055£ 444$ 285"))))
+  (testing "single zero with space is invalid"
+    (is (false? (luhn/valid? " 0"))))
+  (testing "lots of zeros are valid"
+    (is (true? (luhn/valid? " 00000"))))
+  (testing "another valid sin"
+    (is (true? (luhn/valid? "055 444 285"))))
+  (testing "nine doubled is nine"
+    (is (true? (luhn/valid? "091"))))
+)