Writing unit tests for Question2Answer

Question2Answer has a (currently small) unit test suite. Unit tests check ‘units’ of code (functions) in isolation to ensure they all work as expected. We’d like to expand our test coverage as much as possible; here are a few tips for contributing.

Running the unit tests

Testing requires PHPUnit. The latest version of PHPUnit requires PHP 5.6 so most users will want v4.8 which supports PHP 5.3+. For Mac or Linux you can follow these steps:

  1. Download PHPUnit 4.8 (PHP archive file).
  2. Mark it as executable using the command chmod +x phpunit.phar
  3. Move it to your executable directory: mv phpunit.phar /usr/local/bin/phpunit
  4. Navigate to the Question2Answer root directory.
  5. Run phpunit --bootstrap qa-tests/autoload.php qa-tests

Windows users can find detailed instructions here.

Also check out the PHPunit documentation for more information about PHPUnit and unit testing in general.

Writing tests

Unit tests are grouped according to the file in which the original functions reside. For example, tests for function from qa-include/app/users.php are in AppUsersTest.php. The file should contain a class of the same name, like this:

<?php
require_once QA_INCLUDE_DIR.'app/users.php';

class AppUsersTest extends PHPUnit_Framework_TestCase
{
    // test functions go here
}

Note that we include the original app/users.php file so that we can call the functions.

The tests themselves should be named as test__ followed by the original function name. For example, tests for qa_permit_value_error should be in a function test__qa_permit_value_error.

Optionally, multiple tests for the same function may be split into several test functions; each of these should have a suffix consisting of a double underscore and appropriate identifier. For example the tests for qa_block_ip_match are split into test__qa_block_ip_match__ipv4 and test__qa_block_ip_match__ipv6 for testing IPv4 and IPv6 values respectively.

Tests contain assertions, which are functions that compare the result you get from a function with your expected output. The main ones we use are assertEquals to check if two things are equal, assertSame to check they are equal and the same type, and ``assertTrue/assertFalse to check if a result is true/false. Here's an example from UtilStringTest.php`:

<?php
require_once QA_INCLUDE_DIR.'util/string.php';

class UtilStringTest extends PHPUnit_Framework_TestCase
{
    public function test__qa_tags_to_tagstring()
    {
        $test = qa_tags_to_tagstring(array('Hello', 'World'));
        $expected = 'Hello,World';

        $this->assertEquals($expected, $test);
    }
}

Take a look at the PHPUnit docs and our existing tests to see more examples.

Handling options

Tests must be able to run without the database, since of course everyone running the tests does not have the same database. One roadblock to this is Q2A’s options, which are used by many different functions. However, we can make Q2A skip the database by manually setting up an options cache.

First we need to check which options the function we’re testing uses. Then we add some test values to the $qa_options_cache variable. This also means we can test Q2A functions with different configurations of options. Here’s an example from AppUsersTest.php:

public function test__qa_permit_value_error()
{
    // set options cache to bypass database
    global $qa_options_cache;
    $qa_options_cache['confirm_user_emails'] = '1';
    $qa_options_cache['moderate_users'] = '0';

    // run tests using those options...
}