SendInput not working in VS 2008 unit tests

Question

Hello,

I am using SendInput() for the first time, having only heard of it about a week ago. I have written a test using SendInput() to hold down the CTRL key. After a great deal of pain, I got this to work when I run the test using the TestDriven.net tool, an addin for Microsoft Visual Studio:

http://www.testdriven.net/

However, when I run it as a unit test in VS 2008, (right-clicking on the test and choosing "Run Tests" from the menu, or choosing RunSelection from the TestView form), I get a return value of 0 from SendInput().

I'm at a complete loss, thanks for your help.

Here is my code:

[TestMethod]
public void SendInputTest()
{
  Keyboard.NonCharKeyDown(VK.CONTROL);
}


public static void NonCharKeyDown(VK vk)
    {
        INPUT[] inputs = new INPUT[1];
        inputs[0].type = WindowsAPI.INPUT_KEYBOARD;
        inputs[0].ki.dwFlags = 0;
        inputs[0].ki.wVk = (short)vk;
        uint intReturn = WindowsAPI.SendInput(1, inputs, System.Runtime.InteropServices.Marshal.SizeOf(inputs[0]));
        if (intReturn != 1)
        {
            throw new Exception("Could not send key: " + vk);
        } 
    }

public enum VK : short
{
  SHIFT = 0x10,
  CONTROL = 0x11,
  MENU = 0x12
}

[DllImport("user32.dll")]
public static extern IntPtr GetMessageExtraInfo();

public const int INPUT_MOUSE = 0;
public const int INPUT_KEYBOARD = 1;  <---------------
public const int INPUT_HARDWARE = 2;
public const uint KEYEVENTF_EXTENDEDKEY = 0x0001;
public const uint KEYEVENTF_KEYUP = 0x0002;
public const uint KEYEVENTF_UNICODE = 0x0004;
public const uint KEYEVENTF_SCANCODE = 0x0008;
public const uint XBUTTON1 = 0x0001;
public const uint XBUTTON2 = 0x0002;
public const uint MOUSEEVENTF_MOVE = 0x0001;
public const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
public const uint MOUSEEVENTF_LEFTUP = 0x0004;
public const uint MOUSEEVENTF_RIGHTDOWN = 0x0008;
public const uint MOUSEEVENTF_RIGHTUP = 0x0010;
public const uint MOUSEEVENTF_MIDDLEDOWN = 0x0020;
public const uint MOUSEEVENTF_MIDDLEUP = 0x0040;
public const uint MOUSEEVENTF_XDOWN = 0x0080;
public const uint MOUSEEVENTF_XUP = 0x0100;
public const uint MOUSEEVENTF_WHEEL = 0x0800;
public const uint MOUSEEVENTF_VIRTUALDESK = 0x4000;
public const uint MOUSEEVENTF_ABSOLUTE = 0x8000;




[StructLayout(LayoutKind.Sequential)]
public struct KEYBDINPUT
{
  public short wVk;
  public short wScan;
  public uint dwFlags;
  public int time;
  public IntPtr dwExtraInfo;
}

[DllImport("user32.dll")]
public static extern uint SendInput(uint numberOfInputs, [MarshalAs(UnmanagedType.LPArray, SizeConst = 1)] INPUT[] input, int structSize);


public struct INPUT
{
 [FieldOffset(0)]
 public int type;
 [FieldOffset(8)] //*
 public MOUSEINPUT mi;
 [FieldOffset(8)] //*
 public KEYBDINPUT ki;
 [FieldOffset(8)] //*
 public HARDWAREINPUT hi;
}