NUnitで自作クラスのユニットテストを行う ref: http://qiita.com/items/47f09523f1b9dfa015b1

AssemblyInfo.cs

using System.Runtime.CompilerServices;

[assembly: InternalsVisibleTo("RenameAlignDigitTest")]

ClassMyCompare.cs

using System;

namespace Rohinomiya
{
    public class MyCompare
    {
        public MyCompare()
        {
        }

        /// <summary>
        /// 数値 current がlower ～ higher の範囲内か？       
        /// </summary>
        /// <param name="lower">区間(開始)</param>
        /// <param name="current">比較される値</param>
        /// <param name="higher">区間(終了)</param>
        /// <param name="inclusive">閉区間か？(境界値を含む) (初期値:true)</param>
        /// <returns>範囲内であればtrue</returns>
        public static bool Between(int lower, int current, int higher, bool inclusive = true)
        {
            if(lower > higher) Swap(ref lower,ref higher);

            return inclusive ?
                (lower <= current && current <= higher) :
                (lower <  current && current <  higher);
        }

        /// <summary>
        /// ２つの値を交換する
        /// </summary>
        /// <param name="a">値A</param>
        /// <param name="b">値B</param>
        public static void Swap(ref int a, ref int b)
        {
            int temp = a;
            a = b;
            b = temp;
        }
    }
}

ClassMyCompareTest.cs

using System;
using NUnit.Framework;

namespace Rohinomiya
{
    [TestFixture]
    public class MyCompareTest
    {
//      [Test]
//      public void SwapTest()
//      {
//          int a = 3;
//          int b = 5;
//          
//          MyCompare.Swap(ref a,ref b);
//          Assert.AreEqual(5,a);
//          Assert.AreEqual(3,b);
//          
//          a = -1;
//          b = 0;
//          
//          MyCompare.Swap(ref a,ref b);
//          Assert.AreEqual(0,a);
//          Assert.AreEqual(-1,b);
//      }

        [TestCase(3,5,5,3)]
        [TestCase(-1,0,0,-1)]
        public void SwapTest(int expectedA, int expectedB, int a, int b)
        {
            MyCompare.Swap(ref a,ref b);

            Assert.AreEqual(expectedA,a);
            Assert.AreEqual(expectedB,b);
        }

//      [Test]
//      public void BetweenTest()
//      {
//          Assert.AreEqual(true,MyCompare.Between(1,2,3));
//          Assert.AreEqual(true,MyCompare.Between(1,3,3));
//          Assert.AreEqual(true,MyCompare.Between(1,1,3));
//          
//          Assert.AreEqual(false,MyCompare.Between(1,1,3,false));
//          Assert.AreEqual(false,MyCompare.Between(1,3,3,false));
//          Assert.AreEqual(true,MyCompare.Between(1,2,3,false));
//
//          Assert.AreEqual(true,MyCompare.Between(3,2,1));
//          Assert.AreEqual(true,MyCompare.Between(3,3,1));
//          Assert.AreEqual(true,MyCompare.Between(3,1,1));
//          
//          Assert.AreEqual(false,MyCompare.Between(3,1,1,false));
//          Assert.AreEqual(false,MyCompare.Between(3,3,1,false));
//          Assert.AreEqual(true,MyCompare.Between(3,2,1,false));
//      }

        [TestCase(true,1,2,3,true)]
        [TestCase(true,1,3,3,true)]
        [TestCase(true,1,1,3,true)]
        [TestCase(false,1,1,3,false)]
        [TestCase(false,1,3,3,false)]
        [TestCase(true,1,2,3,false)]
        [TestCase(true,3,2,1,true)]
        [TestCase(true,3,3,1,true)]
        [TestCase(true,3,1,1,true)]
        [TestCase(false,3,1,1,false)]
        [TestCase(false,3,3,1,false)]
        [TestCase(true,3,2,1,false)]
        public void BetweenTest(bool expected, int lower, int current, int higher, bool inclusive = true)
        {
            bool result = MyCompare.Between(lower, current, higher, inclusive);
            Assert.AreEqual(expected, result);
        }

    }
}