Update Luhn tests for #161 (#162)

Author: robkeim

exercises/luhn/Example.cs

@@ -1,22 +1,23 @@
 using System;
 using System.Linq;
 
-public class Luhn
+public static class Luhn
 {
-    private readonly long number;
+    public static bool IsValid(string number)
+    {
+        number = number.Replace(" ", "");
 
-    public long CheckDigit { get { return number % 10; } }
-    public int[] Addends { get; private set; }
-    public int Checksum { get { return Addends.Sum(); } }
-    public bool Valid { get { return Checksum % 10 == 0; } }
+        if (number.Length < 2 || number.Any(c => c < '0' || c > '9'))
+        {
+            return false;
+        }
 
-    public Luhn(long number)
-    {
-        this.number = number;
-        Addends = GenerateAddends();
+        var checksum = GenerateChecksum(number);
+
+        return checksum % 10 == 0;
     }
 
-    private int[] GenerateAddends()
+    private static int GenerateChecksum(string number)
     {
         var reversedIntArray = SplitToReversedIntArray(number);
         for (int i = 1; i < reversedIntArray.Length; i++)
@@ -25,34 +26,17 @@ private int[] GenerateAddends()
                 reversedIntArray[i] = ConvertDigitForAddend(reversedIntArray[i]);
         }
         Array.Reverse(reversedIntArray);
-        return reversedIntArray;
+        return reversedIntArray.Sum();
     }
 
-    private static int[] SplitToReversedIntArray(long value)
+    private static int[] SplitToReversedIntArray(string value)
     {
-        return value.ToString().Select(c => int.Parse(c.ToString())).Reverse().ToArray();
+        return value.Select(c => int.Parse(c.ToString())).Reverse().ToArray();
     }
 
     private static int ConvertDigitForAddend(int value)
     {
         var doubled = value * 2;
         return doubled < 10 ? doubled : doubled - 9;
     }
-
-    public static long Create(long number)
-    {
-        var zeroCheckDigitNumber = number * 10;
-        var luhn = new Luhn(zeroCheckDigitNumber);
-
-        if (luhn.Valid)
-            return zeroCheckDigitNumber;
-
-        return zeroCheckDigitNumber + CreateCheckDigit(luhn.Checksum);
-    }
-
-    private static int CreateCheckDigit(int value)
-    {
-        var nearestTen = (int)(Math.Ceiling(value / 10.0m) * 10);
-        return nearestTen - value;
-    }
 }

exercises/luhn/LuhnTest.cs

@@ -3,60 +3,14 @@
 [TestFixture]
 public class LuhnTest
 {
-    [Test]
-    public void Check_digit_is_the_rightmost_digit()
-    {
-        Assert.That(new Luhn(34567).CheckDigit, Is.EqualTo(7));
-    }
-
-    [Ignore("Remove to run test")]
-    [Test]
-    public void Addends_doubles_every_other_number_from_the_right()
-    {
-        Assert.That(new Luhn(12121).Addends, Is.EqualTo(new[] { 1, 4, 1, 4, 1 }));
-    }
-
-    [Ignore("Remove to run test")]
-    [Test]
-    public void Addends_subtracts_9_when_doubled_number_is_more_than_9()
-    {
-        Assert.That(new Luhn(8631).Addends, Is.EqualTo(new[] { 7, 6, 6, 1 }));
-    }
-
-    [Ignore("Remove to run test")]
-    [TestCase(4913, ExpectedResult = 22)]
-    [TestCase(201773, ExpectedResult = 21)]
-    public int Checksum_adds_addends_together(int number)
-    {
-        return new Luhn(number).Checksum;
-    }
-
-    [Ignore("Remove to run test")]
-    [TestCase(738, ExpectedResult = false)]
-    [TestCase(8739567, ExpectedResult = true)]
-    public bool Number_is_valid_when_checksum_mod_10_is_zero(int number)
-    {
-        return new Luhn(number).Valid;
-    }
-
-    [Ignore("Remove to run test")]
-    [Test]
-    public void Luhn_can_create_simple_numbers_with_valid_check_digit()
-    {
-        Assert.That(Luhn.Create(123), Is.EqualTo(1230));
-    }
-
-    [Ignore("Remove to run test")]
-    [Test]
-    public void Luhn_can_create_larger_numbers_with_valid_check_digit()
-    {
-        Assert.That(Luhn.Create(873956), Is.EqualTo(8739567));
-    }
-
-    [Ignore("Remove to run test")]
-    [Test]
-    public void Luhn_can_create_huge_numbers_with_valid_check_digit()
-    {
-        Assert.That(Luhn.Create(837263756), Is.EqualTo(8372637564));
+    [TestCase("1", ExpectedResult = false)] // single digit strings can not be valid
+    [TestCase("0", ExpectedResult = false, Ignore = "Remove to run test")] // a single zero is invalid
+    [TestCase("046 454 286", ExpectedResult = true, Ignore = "Remove to run test")] // valid Canadian SIN
+    [TestCase("046 454 287", ExpectedResult = false, Ignore = "Remove to run test")] // invalid Canadian SIN
+    [TestCase("8273 1232 7352 0569", ExpectedResult = false, Ignore = "Remove to run test")] // invalid credit card
+    [TestCase("827a 1232 7352 0569", ExpectedResult = false, Ignore = "Remove to run test")] // strings that contain non-digits are not valid
+    public bool ValidateChecksum(string number)
+    {
+        return Luhn.IsValid(number);
     }
 }