This is how I unit test.

gistfile1.cpp

#include "image.hpp"
#include "sprite_sheet.hpp"
#include "raster_font.hpp"
#include "surface_manager.hpp"
#include "button.hpp"

#include "SDL/SDL.h"

#include <iostream>
#include <chrono>

using namespace std;

int main(int, char**) {
  SDL_Init(0);
	SDL_Surface* screen = SDL_SetVideoMode(640, 480, 32, SDL_HWSURFACE|SDL_DOUBLEBUF);
	SurfaceManager surfaceMgr;

	surfaceMgr.Load("player","elliot2.bmp");
	surfaceMgr.Load("font","pokemon_dark_font.bmp");
	surfaceMgr.Load("button","button.bmp");

	Image image(surfaceMgr["font"]);
	SpriteSheet ssheet(surfaceMgr["player"], 32, 48);
	RasterFont font(surfaceMgr["font"]);
	Button button(300, 300, surfaceMgr["button"], surfaceMgr["font"], "button");

	ssheet.SetInterval(0.1);

	typedef std::chrono::high_resolution_clock Clock;
	Clock::time_point point = Clock::now();

	bool running = true;
	while(running) {
		SDL_Event event;
		while (SDL_PollEvent(&event)) {
			switch(event.type) {
				case SDL_QUIT:
					running = false;
				break;
				case SDL_MOUSEMOTION:
					button.MouseMotion(event.motion);
				break;
				case SDL_MOUSEBUTTONDOWN:
					button.MouseButtonDown(event.button);
				break;
				case SDL_MOUSEBUTTONUP:
					button.MouseButtonUp(event.button);
				break;
				case SDL_KEYDOWN:
					//
				break;
				case SDL_KEYUP:
					//
				break;
			}
		}
		//update
		ssheet.Update(double((Clock::now()-point).count()) / Clock::period::den);
		point = Clock::now();

		//draw
		SDL_FillRect(screen, 0, 0);
//		image.DrawTo(screen, 0, 0);
		font.DrawStringTo("hello world", screen, 100, 100);
		ssheet.DrawTo(screen, 200, 200);
		button.DrawTo(screen);
		SDL_Flip(screen);
	}

	surfaceMgr.FreeAll();

	SDL_Quit();
	return 0;
}