FizzBuzz-Kata-2018-07-11.cs

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

namespace UnitTestProject1
{
    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void Test1ReturnsStringOne()
        {
            var subject = new FizzBuzzer();
            var result = subject.Emit(1);
            result.Should().Be("1");
        }

        [TestMethod]
        public void TestMultiplesOf3ReturnStringFizz()
        {
            var subject = new FizzBuzzer();
            var A_MULTIPLE_OF_THREE = 2 * 3;
            var result = subject.Emit(A_MULTIPLE_OF_THREE);
            result.Should().Be("Fizz");
        }

        [TestMethod]
        public void TestMultiplesOf5ReturnStringBuzz()
        {
            var subject = new FizzBuzzer();
            var A_MULTIPLE_OF_FIVE = 2 * 5;
            var result = subject.Emit(A_MULTIPLE_OF_FIVE);
            result.Should().Be("Buzz");
        }

        [TestMethod]
        public void TestMultiplesOf3And5ReturnStringFizzBuzz()
        {
            var subject = new FizzBuzzer();
            var A_MULTIPLE_OF_THREE_AND_FIVE = 3 * 5;
            var result = subject.Emit(A_MULTIPLE_OF_THREE_AND_FIVE);
            result.Should().Be("FizzBuzz");
        }
    }

    public class FizzBuzzer
    {
        public string Emit(int value)
        {

            if (value.IsMultipleOf(3 * 5))
            {
                return "FizzBuzz";
            }

            if (value.IsMultipleOf(3))
            {
                return "Fizz";
            }

            if (value.IsMultipleOf(5))
            {
                return "Buzz";
            }
            return value.ToString();
        }
    }

    public static class Extensions
    {
        public static bool IsMultipleOf(this int @this, int divisor) => @this % divisor == 0;
    }
}