We've covered Fizz. We've covered Buzz. And, we've covered FizzBuzz. Now we must account for numbers that are divisible by neither 3 nor 5.  Remember, in the event that a number is divisible by neither 3 nor 5, we simply return the number supplied. Let's take a look at this test:

[Fact]
public void Given1Then1()
{
  // Arrange
  // Act 
  var result = FizzBuzz(1);

  // Assert 
  Assert.Equal(1, result);
}