function diffTest(&$session)
{
    $x2 = "a\nx\ny\nz\nb";
    $x1 = "a\nb";
    $x2 = "x\ny\nb";
    $x1 = "m\nb";
    $x2 = "m";
    $x1 = "x\ny";
    guiParagraph($session, str_replace("\n", "<br>", $x1), false);
    guiParagraph($session, str_replace("\n", "<br>", $x2), false);
    $engine = new DiffEngine($session, $x1, $x2);
    $engine->compare(1, 1);
}