Just in order so we see it I include an example where I removed the failing test and in the following example all of the assertions are successful.

examples/php/simpletest/st02.php
<?php

require_once(dirname(__FILE__) . '/../../../tools/simpletest/autorun.php');

require_once(dirname(__FILE__) . '/../includes/mylib.php');

class TestOfAdd extends UnitTestCase {
    function testAdd() {
        $this->assertTrue(add(1,1) == 2);
        $this->assertTrue(add(2,2) == 4);
    }
}


?>


Output:

examples/php/simpletest/st02.txt
st02.php
1/1 test cases complete: 2 passes, 0 fails and 0 exceptions.

With the last row being GREEN