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TDD: Test Driven Drupal
#######################

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Oliver Davies (@opdavies)

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https://opdavi.es/drupal-london

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Software Developer, Consultant, open-source maintainer

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  TextAnnotation "I develop and consult on Drupal applications for clients."
  TextAnnotation "I contribute to and maintain open-source projects including Drupal core."
  TextAnnotation "Different perspectives."

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  TextAnnotation "I saw this tweet by Tim Millwood and become the maintainer in 2012."

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   TextAnnotation "These were the usage statistics from Drupal.org when I became the maintainer."

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    TextAnnotation "173rd most used module on Drupal.org"
    TextAnnotation "~38,000 sites - ~13,000 D7 and ~24,000 D8/9/10"

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   TextAnnotation "Had some existing tests, crucial to preventing regressions"

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Why write tests?
================

* Peace of mind
* Prevent regressions
* Catch bugs earlier
* Write less code
* Documentation
* Drupal core requirement
* More important with regular D10/D11 releases and supporting multiple versions

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    TextAnnotation "I don't want to break 38,000 Drupal sites when rolling a new release, or causing a regression in a client codebase."
    TextAnnotation "TDD often results in writing less code as you're figuring things out whilst writing the test, only writing code that's needed for the tests."
    TextAnnotation "Drupal core gates. Testing gate requires new tests for new features, failing test cases for bug fixes, and code coverage when refactoring code."
    TextAnnotation "Same projects can work for Drupal 8, 9 and 10 etc."

Testing in Drupal
=================

* **Drupal 7** - SimpleTest (testing) module provided as part of core
* **Drupal 8** - PHPUnit added as a core dependency, later became the default via the PHPUnit initiative
* **Drupal 9** - SimpleTest removed from core, moved back to contrib

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   TextAnnotation "Not speaking about Drupal 7 and SimpleTest in this talk, but a lot of the concepts are the same."

Writing PHPUnit Tests for Drupal
================================

* PHP class with ``.php`` extension
* ``tests/src`` directory within each module
* Within the ``Drupal\Tests\{module_name}`` namespace
* Class name must match the filename
* Namespace must match the directory structure
* One test class per feature

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    TextAnnotation "Tests per module."
    TextAnnotation "PSR-4 autoloading."
    TextAnnotation "Different to D7."

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Arrange, Act, Assert

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   TextAnnotation "What are the parts of a test?"
   TextAnnotation ""
   TextAnnotation "Set up the world, perform an action, then make assertions."

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Given, When, Then

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  TextAnnotation "Given the About page exists..."
  TextAnnotation "When I go to that page..."
  TextAnnotation "I should see 'About me' on the page."

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What to test?
=============

* Creating nodes with data from an API
* Calculating attendance figures for an event
* Determining if an event is purchasable
* Promotions and coupons for new users
* Cloning events
* Queuing private message requests
* Re-opening closed support tickets when comments are added

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  TextAnnotation "Examples of some things that I tested on previous projects."

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What does a test look like?
===========================

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What does a test look like?
===========================

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What does a test look like?
===========================

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What does a test look like?
===========================

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What does a test look like?
===========================

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Writing test methods
====================

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Writing test methods
====================

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Writing test methods
====================

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Writing test methods
====================

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Types of Tests
==============

* **Functional/FunctionalJavascript** (web, browser, feature)
* **Kernel** (integration)
* **Unit**

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   TextAnnotation "Not just unit tests."

Functional Tests
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* Tests end-to-end functionality
* UI testing
* Interacts with database
* Full Drupal installation
* Slower to run
* With/without JavaScript

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   TextAnnotation "Uses the `testing` profile with a fresh installation between tests."

Kernel tests
============

* Integration tests
* Can install modules, interact with services, container, database
* Minimal Drupal bootstrap
* Faster than functional tests
* More setup required

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    TextAnnotation "Can still access services like \Drupal::messenger()."

Unit Tests
==========

* Tests PHP logic
* No database interaction
* Fast to run
* Need to mock dependencies
* Can become tightly coupled
* Can be hard to refactor

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Running Tests

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Core script
===========

.. code-block:: shell

    $ php web/core/scripts/run-tests.sh

    $ php web/core/scripts/run-tests.sh \
      --all

    $ php web/core/scripts/run-tests.sh \
      --module example

    $ php web/core/scripts/run-tests.sh \
      --class ExampleTest

Core script
===========

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    $ php web/core/scripts/run-tests.sh \
      --module example \
      --sqlite /dev/shm/test.sqlite \
      --url http://web

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    Drupal test run
    ---------------

    Tests to be run:
      - Drupal\Tests\example\Functional\ExamplePageTest

    Test run started:
      Saturday, October 14, 2023 - 10:28

    Test summary
    ------------

    Drupal\Tests\example\Functional\ExamplePageTest                1 passes

    Test run duration: 7 sec

PHPUnit
=======

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   $ export SIMPLETEST_BASE_URL=http://web

   $ web/vendor/bin/phpunit \
    -c web/core \
    modules/contrib/examples/modules/phpunit_example 

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    TextAnnotation "Update the phpunit path and config file path for your project."
    TextAnnotation "-c not needed if the phpunit.xml.dist or phpunit.xml is in the same directory."

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    PHPUnit 9.6.13 by Sebastian Bergmann and contributors.

    Testing /app/web/modules/contrib/examples/modules/phpunit_example
    .................................                                 33 / 33 (100%)

    Time: 00:08.660, Memory: 10.00 MB

    OK (33 tests, 43 assertions)

Creating a phpunit.xml file
===========================

- Configures PHPUnit
- Needed to run some types of tests
- Ignored by Git by default
- Copy ``core/phpunit.xml.dist`` to ``core/phpunit.xml``
- Add and change as needed

    - ``SIMPLETEST_BASE_URL``, ``SIMPLETEST_DB``, ``BROWSERTEST_OUTPUT_DIRECTORY``
    - ``stopOnFailure="true"``

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   TextAnnotation "For core. For projects, I create a customised phpunit.xml.dist in my project."

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Test Driven Development
=======================

* Write a failing test
* Write code until the test passes
* Refactor
* Repeat

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    TextAnnotation "Write enough of a test so that it fails."
    TextAnnotation "Write enough code so that the test passes."
    TextAnnotation "Refactor if needed."
    TextAnnotation "Repeat."

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Red, Green, Refactor

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Porting Modules From Drupal 7
=============================

- Make a new branch
- Add/update the tests
- Write code to make the tests pass
- Refactor
- Repeat

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    TextAnnotation "Similar to the TDD workflow."

How I Write Tests - "Outside In"
================================

- Start with functional tests
- Drop down to integration or unit tests where needed
- Programming by wishful thinking
- Write comments first, then fill in the code
- Sometimes write assertions first

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    TextAnnotation "Write the code in your test that you wish you had, and let the tests tell you what's missing."


How I Write Tests - "Outside In"
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* Functional - 57 tests, 180 assertions
* Kernel - 38 tests, 495 assertions
* Unit - 5 tests, 18 assertions

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Run in 2-3 minutes in a CI pipeline with GitHub Actions.

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Thanks!
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References:

* https://phpunit.de
* https://docs.phpunit.de
* https://www.drupal.org/docs/automated-testing

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Me:

* https://www.oliverdavies.uk
* https://www.oliverdavies.uk/drupal-london
* https://www.oliverdavies.uk/atdc