Coin Changer kata with Map in C# using MS Test

CoinChangerTests.cs

using System;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace CoinChanger
{
    [TestClass]
    public class CoinChangerTests
    {
        [TestMethod]
        [ExpectedException(typeof(ArgumentException))]
        public void GivenNoCoins_WhenChangeForIsGiven0_ItMustThrowAnArgumentException()
        {
            var target = new CoinChanger();

            target.ChangeFor(0);
        }

        [TestMethod]
        [ExpectedException(typeof(ArgumentException))]
        public void GivenNoCoins_WhenChangeForIsGiven1_ItMustThrowAnArgumentException()
        {
            var target = new CoinChanger();

            target.ChangeFor(1);
        }

        [TestMethod]
        public void GivenPennies_WhenChangeForIsGiven0_ItMustReturn0Pennies()
        {
            var target = new CoinChanger{Coins = new []{1}};

            var actual = target.ChangeFor(0);

            var expected = new[] { 0 };
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenPennies_WhenChangeForIsGiven1_ItMustReturn1Penny()
        {
            var target = new CoinChanger{Coins = new []{1}};

            var actual = target.ChangeFor(1);

            var expected = new[] {1};
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenPennies_WhenChangeForIsGiven4_ItMustReturn4Pennies()
        {
            var target = new CoinChanger{Coins = new []{1}};

            var actual = target.ChangeFor(4);

            var expected = new[] {4};
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenNickels_WhenChangeForIsGiven5_ItMustReturn1Nickel()
        {
            var target = new CoinChanger{Coins = new []{5}};

            var actual = target.ChangeFor(5);

            var expected = new[] {1};
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenNickelsAndPennies_WhenChangeForIsGiven5_ItMustReturn1NickelAnd0Pennies()
        {
            var target = new CoinChanger{Coins = new []{5, 1}};

            var actual = target.ChangeFor(5);

            var expected = new[] {1, 0};
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenDimesNickelsAndPennies_WhenChangeForIsGiven17_ItMustReturn1Dime1NickelAnd2Pennies()
        {
            var target = new CoinChanger{Coins = new []{10, 5, 1}};

            var actual = target.ChangeFor(17);

            var expected = new[] {1, 1, 2};
            CollectionAssert.AreEqual(expected, actual);
        }

        [TestMethod]
        public void GivenQuartersDimesNickelsAndPennies_WhenChangeForIsGiven99_ItMustReturn3Quarters2Dimes0NickelsAnd4Pennies()
        {
            var target = new CoinChanger{Coins = new []{25, 10, 5, 1}};

            var actual = target.ChangeFor(99);

            var expected = new[] {3, 2, 0, 4};
            CollectionAssert.AreEqual(expected, actual);
        }
    }

    public class CoinChanger
    {
        public int[] Coins { get; set; }

        public int[] ChangeFor(int amount)
        {
            if (Coins == null) throw new ArgumentException("No coins");
            
            return Coins.Select(coin =>
            {
                var result = amount/coin;
                amount %= coin;
                return result;
            }).ToArray();
        }
    }
}