While it is nice to know we'll be able to test each one of the functions or classes on its own in many cases that's not how things work. For this testing method to work yo have to be able to separate the functionality of each function and class and test them in isolation.

Especially when you already have a partially or fully working application probably written by someone else who wrote spaghetti code, it would be impossible to write tests in isolation. It will be probably also a waste of energy as soon you are going to start to clean up that code changing the internal structure, changing how functions work and building up - hopefully - a cleaner codebase.

In such cases it is much better to start from the top down. Test the functionality of the application without even knowing about the internal structure of the code. Actually the application does not even need to be written in PHP for this type of testing.

We are going to imitate the web browser, access a web site and check if the returned page contains the information as we expect.

We subclass the WebTestCase class which provides a get method to retrieve a web page given a URL. In itself that's not yet an assertion so we wrap it with the already familiar assertTrue method. We can do that as WebTestClass is a subclass of UnitTestCase.

examples/php/simpletest/web01.php
<?php

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


class TestOfCalculator extends WebTestCase {
    function testBasicCalc() {
        $url = 'http://localhost:8081/php/calc/basic_calc.php';
        $this->assertTrue($this->get($url));
    }
}


?>

The resulting output is similar to what we saw earlier when we just tried to test an internal function.