convert this C++ program into a C program.. include the stdio.h and etc.

namespace HelloWorldTests

{

[TestClass]

public class UnitTest1

{

private const string Expected = "Hello World!";

[TestMethod]

public void TestMethod1()

{

using (var sw = new StringWriter())

{

Console.SetOut(sw);

HelloWorldCore.Program.Main();

var result = sw.ToString().Trim();

Assert.AreEqual(Expected, result);

}

}

}

}