Advanced Unit Testing, Part IV - Fixture Setup/Teardown, Test Repetition And Performance Tests

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;

using UnitTest;

namespace UTExample
{
	[TestFixture]
	public class TimerTest
	{
		[Test]
		public void TenMilliSecondAccuracy()
		{
			double startTime=HiResTimer.Ticks;
			Thread.Sleep(10);
			double stopTime=HiResTimer.Ticks;
			double t=(stopTime-startTime)/HiResTimer.TicksPerSecond;
			Assertion.Assert(t >= .0095 && t<=.0105, "Accuracy problem: "+t.ToString());
		}

		[Test]
		public void OneSecondAccuracy()
		{
			double startTime=HiResTimer.Ticks;
			Thread.Sleep(1000);
			double stopTime=HiResTimer.Ticks;
			double t=(stopTime-startTime)/HiResTimer.TicksPerSecond;
			Assertion.Assert(t >= .99 && t<=1.01, "Accuracy problem: "+t.ToString());
		}

		[Test]
		public void Resolution()
		{
			long n1=HiResTimer.Ticks;
			long n2;
			long n3;

			// sync
			while (n1 == (n2=HiResTimer.Ticks)) {}

			// wait
			while (n2 == (n3=HiResTimer.Ticks)) {}
			double q=n3-n2;
			// q==156250
			double sec=(double)q/HiResTimer.TicksPerSecond;
			Assertion.Assert(sec<=0.0000007, "Insufficient resolution: "+sec.ToString());
		}
	}

	// the wrong way, using DateTime
//	public class HiResTimer
//	{
//		public static long Ticks
//		{
//			get {return DateTime.Now.Ticks;}
//		}
//
//		public static long TicksPerSecond
//		{
//			get {return TimeSpan.TicksPerSecond;}
//		}
//	}

	// the right way, using QueryPerformanceFrequency
	public class HiResTimer
	{
		[DllImport("Kernel32.dll")]
		private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);

		[DllImport("Kernel32.dll")]
		private static extern bool QueryPerformanceFrequency(out long lpFrequency);

		public static long Ticks
		{
			get
			{
				long t;
				QueryPerformanceCounter(out t);
				return t;
			}
		}

		public static long TicksPerSecond
		{
			get
			{
				long freq;
				QueryPerformanceFrequency(out freq);
				return freq;
			}
		}
	}
}