Setting up Drupal on ddev for drupal core contributions

Drupal is an open-source content management system that relies on the contributions of its passionate community to thrive and evolve. If you're interested in contributing to Drupal Core, you'll need a development environment that allows you to work efficiently and effectively. One popular choice for creating a local development environment for Drupal is DDEV. In this article, we'll walk you through the process of setting up Drupal on DDEV for Drupal Core contributions.

Before you start, you have ddev and composer installed on your local.

I usually setup drupal codebase using composer and then add ddev config on top of it.

composer create-project drupal/recommended-project drupal10
cd drupal10
ddev config

Then install the required packages for running phpunit tests.

ddev composer require --dev drupal/core-dev jonathanjfshaw/phpunitbehat phpunit/phpunit

Create the required folders.

mkdir -p web/sites/simpletest/browser_output

Copy the core/phpunit.xml.dist to core/phpunit.xml. It should look something like this:
 

<?xml version="1.0" encoding="UTF-8"?>

<!-- For how to customize PHPUnit configuration, see core/tests/README.md. -->
<!-- TODO set checkForUnintentionallyCoveredCode="true" once https://www.drupal.org/node/2626832 is resolved. -->
<!-- PHPUnit expects functional tests to be run with either a privileged user
 or your current system user. See core/tests/README.md and
 https://www.drupal.org/node/2116263 for details.
-->
<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         bootstrap="tests/bootstrap.php" colors="true"
         beStrictAboutTestsThatDoNotTestAnything="true"
         beStrictAboutOutputDuringTests="true"
         beStrictAboutChangesToGlobalState="true"
         failOnWarning="true"
         printerClass="\Drupal\Tests\Listeners\HtmlOutputPrinter"
         cacheResult="false"
         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
  <php>
    <!-- Set error reporting to E_ALL. -->
    <ini name="error_reporting" value="32767"/>
    <!-- Do not limit the amount of memory tests take to run. -->
    <ini name="memory_limit" value="-1"/>
    <!-- Example SIMPLETEST_BASE_URL value: http://localhost -->
    <env name="SIMPLETEST_BASE_URL" value="https://drupal10.ddev.site"/>
    <!-- Example SIMPLETEST_DB value: mysql://username:password@localhost/databasename#table_prefix -->
    <env name="SIMPLETEST_DB" value="mysql://db:db@db/db"/>
    <!-- Example BROWSERTEST_OUTPUT_DIRECTORY value: /path/to/webroot/sites/simpletest/browser_output -->
    <env name="BROWSERTEST_OUTPUT_DIRECTORY" value="/var/www/html/web/sites/simpletest/browser_output"/>
    <!-- By default, browser tests will output links that use the base URL set
     in SIMPLETEST_BASE_URL. However, if your SIMPLETEST_BASE_URL is an internal
     path (such as may be the case in a virtual or Docker-based environment),
     you can set the base URL used in the browser test output links to something
     reachable from your host machine here. This will allow you to follow them
     directly and view the output. -->
    <env name="BROWSERTEST_OUTPUT_BASE_URL" value=""/>

    <!-- Deprecation testing is managed through Symfony's PHPUnit Bridge.
      The environment variable SYMFONY_DEPRECATIONS_HELPER is used to configure
      the behaviour of the deprecation tests.
      See https://symfony.com/doc/current/components/phpunit_bridge.html#configuration
      Drupal core's testing framework is setting this variable to its defaults.
      Projects with their own requirements need to manage this variable
      explicitly.
    -->
    <!-- To disable deprecation testing completely uncomment the next line. -->
    <!-- <env name="SYMFONY_DEPRECATIONS_HELPER" value="disabled"/> -->
    <!-- Deprecation errors can be selectively ignored by specifying a file of
      regular expression patterns for exclusion.
      See https://symfony.com/doc/current/components/phpunit_bridge.html#ignoring-deprecations
      Uncomment the line below to specify a custom deprecations ignore file.
      NOTE: it may be required to specify the full path to the file to run tests
      correctly.
    -->
    <!-- <env name="SYMFONY_DEPRECATIONS_HELPER" value="ignoreFile=.deprecation-ignore.txt"/> -->

    <!-- Example for changing the driver class for mink tests MINK_DRIVER_CLASS value: 'Drupal\FunctionalJavascriptTests\DrupalSelenium2Driver' -->
    <env name="MINK_DRIVER_CLASS" value=''/>
    <!-- Example for changing the driver args to mink tests MINK_DRIVER_ARGS value: '["http://127.0.0.1:8510"]' -->
    <env name="MINK_DRIVER_ARGS" value=''/>
    <!-- Example for changing the driver args to webdriver tests MINK_DRIVER_ARGS_WEBDRIVER value: '["chrome", { "chromeOptions": { "w3c": false } }, "http://localhost:4444/wd/hub"]' For using the Firefox browser, replace "chrome" with "firefox" -->
    <env name="MINK_DRIVER_ARGS_WEBDRIVER" value=''/>
  </php>
  <testsuites>
    <testsuite name="unit">
      <file>./tests/TestSuites/UnitTestSuite.php</file>
    </testsuite>
    <testsuite name="kernel">
      <file>./tests/TestSuites/KernelTestSuite.php</file>
    </testsuite>
    <testsuite name="functional">
      <file>./tests/TestSuites/FunctionalTestSuite.php</file>
    </testsuite>
    <testsuite name="functional-javascript">
      <file>./tests/TestSuites/FunctionalJavascriptTestSuite.php</file>
    </testsuite>
    <testsuite name="build">
      <file>./tests/TestSuites/BuildTestSuite.php</file>
    </testsuite>
  </testsuites>
  <listeners>
    <listener class="\Drupal\Tests\Listeners\DrupalListener">
    </listener>
  </listeners>
  <!-- Settings for coverage reports. -->
  <coverage>
    <include>
      <directory>./includes</directory>
      <directory>./lib</directory>
      <directory>./modules</directory>
      <directory>../modules</directory>
      <directory>../sites</directory>
    </include>
    <exclude>
      <directory>./modules/*/src/Tests</directory>
      <directory>./modules/*/tests</directory>
      <directory>../modules/*/src/Tests</directory>
      <directory>../modules/*/tests</directory>
      <directory>../modules/*/*/src/Tests</directory>
      <directory>../modules/*/*/tests</directory>
      <directory suffix=".api.php">./lib/**</directory>
      <directory suffix=".api.php">./modules/**</directory>
      <directory suffix=".api.php">../modules/**</directory>
    </exclude>
  </coverage>
</phpunit>

To see if it works, run the following: