FizzBuzz.cs

namespace FizzBuzzChecker
{
        public string[] CheckForFizzBuzz(int[] inputs)
        {
            int counter = 0;
            string[] output = new string[inputs.Length];

            foreach (var number in inputs)
            {
                string tempString = String.Empty;

                //I still think 0 should print 0 but that's just me.

                if (number % 3 == 0) { tempString += "Fizz"; }
                if (number % 5 == 0) { tempString += "Buzz"; }
                if (tempString == String.Empty) { tempString += number.ToString(); }

                output[counter] += tempString;
                counter++;
            }

            return output;
        }
}

FizzBuzz.Test.cs

using Xunit;

namespace FizzBuzzChecker.Test
{
    public class FizzBuzzTests
    {
        [InlineData(3, "Fizz")]
        [InlineData(6, "Fizz")]
        [InlineData(9, "Fizz")]
        [InlineData(12, "Fizz")]
        [Theory]
        public void PrintsFizzWhenTheRemainderIsAMultipleOfThree(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.Equal(expected, actual[0]);
        }

        [InlineData(2, "Fizz")]
        [InlineData(4, "Fizz")]
        [InlineData(7, "Fizz")]
        [InlineData(8, "Fizz")]
        [Theory]
        public void DoesNotPrintFizzWhenTheRemainderIsNotAMultipleOfThree(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.NotEqual(expected, actual[0]);
        }

        [InlineData(5, "Buzz")]
        [InlineData(10, "Buzz")]
        [InlineData(20, "Buzz")]
        [InlineData(500, "Buzz")]
        [Theory]
        public void PrintsBuzzWhenTheRemainderIsAMultipleOfFive(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.Equal(expected, actual[0]);
        }

        [InlineData(3, "Buzz")]
        [InlineData(6, "Buzz")]
        [InlineData(9, "Buzz")]
        [InlineData(12, "Buzz")]
        [Theory]
        public void DoesNotPrintBuzzWhenTheRemainderIsNotAMultipleOfFive(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.NotEqual(expected, actual[0]);
        }

        [InlineData(15, "FizzBuzz")]
        [InlineData(30, "FizzBuzz")]
        [InlineData(45, "FizzBuzz")]
        [InlineData(60, "FizzBuzz")]
        [Theory]
        public void PrintsFizzBuzzWhenTheRemainderIsAMultipleOfThreeAndFive(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.Equal(expected, actual[0]);
        }

        [InlineData(1, "FizzBuzz")]
        [InlineData(9, "FizzBuzz")]
        [InlineData(3, "FizzBuzz")]
        [InlineData(6, "FizzBuzz")]
        [Theory]
        public void DoesNotPrintsFizzBuzzWhenTheRemainderIsNotAMultipleOfThreeAndFive(int numberToCheck, string expected)
        {
            FizzBuzz sut = new FizzBuzz();
            string[] actual = sut.CheckForFizzBuzz(new int[] { numberToCheck });

            Assert.NotEqual(expected, actual[0]);
        }

        private static int[] GenerateTestNumbers()
        {
            int[] output = new int[1000];
            for (int i = 0; i < output.Length; i++)
            {
                output[i] = i;
            }

            return output;
        }
    }
}