public static PageLoader updatePage(Page page) {
    Preconditions.checkArgument(!page.isEmpty(), "Page cannot be empty");
    PageLoader update = new PageLoader();
    update.action = Action.UPDATE;
    update.page = page;
    return update;
  }

package webindex.fluo;

import org.junit.Test;

import webindex.core.models.Page;
import webindex.data.fluo.PageLoader;

public class PageLoaderTest {

	@Test
	public void testNullPage() {
		Page p = null;
		PageLoader loader = PageLoader.updatePage(p);
	}
	
	@Test(expected = IllegalArgumentException.class)
	public void testEmptyPageThrowsIllegalArgument() {
		Page p = Page.EMPTY;
		PageLoader loader = PageLoader.updatePage(p);
	}

}