FizzBuzz kata in C# using FsCheck with MS Test

FizzBuzzerTests.cs

using FsCheck.Fluent;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace FizzBuzz
{
    [TestClass]
    public class FizzBuzzerTests
    {
        [TestMethod]
        public void GivenAnEvenNumber_ResultMustBeSelfAsString()
        {
            Spec.ForAny<int>(x => true)
                .Label("Even must return self as string")
                .And(x => FizzBuzzer.ValueOf(x) == x.ToString())
                .When(x => x%2 == 0 && x%3 != 0 && x%5 != 0)
                .QuickCheckThrowOnFailure();
        }

        [TestMethod]
        public void GivenNumberDivisibleBy3_ResultMustContainFizz()
        {
            Spec.ForAny<int>(x => true)
                .Label("Numbers divisible by 3 must contain Fizz")
                .And(x => FizzBuzzer.ValueOf(x).Contains("Fizz"))
                .When(x => x%3 == 0)
                .QuickCheckThrowOnFailure();
        }

        [TestMethod]
        public void GivenNumberDivisibleBy5_ResultMustContainBuzz()
        {
            Spec.ForAny<int>(x => true)
                .Label("Numbers divisible by 5 must contain Buzz")
                .And(x => FizzBuzzer.ValueOf(x).Contains("Buzz"))
                .When(x => x%5 == 0)
                .QuickCheckThrowOnFailure();
        }

        [TestMethod]
        public void GivenNumberDivisibleBy15_ResultMustBeFizzBuzz()
        {
            Spec.ForAny<int>(x => true)
                .Label("Numbers divisible by 15 must be FizzBuzz")
                .And(x => FizzBuzzer.ValueOf(x * 15).Contains("FizzBuzz"))
                .QuickCheckThrowOnFailure();
        }

        [TestMethod]
        public void GivenNumberNotDivisibleBy3Or5_ResultMustBeSelfAsString()
        {
            Spec.ForAny<int>(x => true)
                .Label("Numbers not divisible by 3 or 5 must be self as string")
                .And(x => FizzBuzzer.ValueOf(x) == x.ToString())
                .When(x => x%3 != 0 && x % 5 != 0)
                .QuickCheckThrowOnFailure();
        }
    }

    public class FizzBuzzer
    {
        public static string ValueOf(int value)
        {
            var result = string.Empty;

            if (value % 3 == 0) result += "Fizz";
            if (value % 5 == 0) result += "Buzz";

            return string.IsNullOrEmpty(result) ? value.ToString() : result;
        }
    }
}