This is a simple sketch I used to test the refresh rate of an Adafruit 2.2" TFT display on an Arduino Mega 2560. http://www.adafruit.com/products/1480

tft_test.ino

#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9340.h"

#if defined(__SAM3X8E__)
    #undef __FlashStringHelper::F(string_literal)
    #define F(string_literal) string_literal
#endif

// These are the pins used for the Mega
// for Due/Uno/Leonardo use the hardware SPI pins (which are different)
#define _sclk 52
#define _miso 50
#define _mosi 51
#define _cs 53
#define _rst 9
#define _dc 8

Adafruit_ILI9340 tft = Adafruit_ILI9340(_cs, _dc, _rst);

void setup() {
  tft.begin();
  tft.setRotation(1);
  tft.fillScreen(ILI9340_BLACK);
  tft.fillRect(120, 70, 115, 70, ILI9340_RED);
  tft.setTextColor(ILI9340_WHITE);
}

void loop(void) {
  tft.setCursor(120, 70);
  tft.setTextSize(10);
  tft.print(millis()/1000);
  delay(999);
  tft.fillRect(120, 70, 115, 70, ILI9340_RED);
  //tft.fillScreen(ILI9340_BLACK); //This is very slow
}