TestNG does not run, shows java.lang.NullPointerException

Question

I am using Eclipse Luna and i have written this basic code.

package TestNg;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.testng.annotations.Test;

public class NewTest {
    WebDriver driver;
  @Test
  public void f() {
      driver =new FirefoxDriver();
      driver.get("http://www.spicejet.com/");
      driver.manage().window().maximize();
  }
}

But when i try to run the test as "Run as TestNG test" i get the below error.

Please find the screenshot