Add instructions for testing contributions in the CONTRIBUTING.md file. (#40018)

Checks ran after closing and opening the PR. One failed but it passed after re-run. Checked and appeard the old anchors were not used in other places so merging this one - thanks!

.github/CONTRIBUTING.md

@@ -37,6 +37,10 @@ Please take a moment to review the [project readme](https://github.com/woocommer
 - Run our build process described in the document on [how to set up WooCommerce development environment](https://github.com/woocommerce/woocommerce/wiki/How-to-set-up-WooCommerce-development-environment), it will install our pre-commit hook, code sniffs, dependencies, and more.
 - Before pushing commits to GitHub, check your code against our code standards. For PHP code in the WooCommerce Core project you can do this by running `pnpm --filter=woocommerce run lint:php:changes:branch`.
 - Whenever possible, please fix pre-existing code standards errors in code that you change.
+- Please consider adding appropriate tests related to your change if applicable such as unit, API and E2E tests. You can check the following guides for this purpose:
+  - [Writing unit tests](https://github.com/woocommerce/woocommerce/blob/trunk/plugins/woocommerce/tests/README.md#guide-for-writing-unit-tests).
+  - [Writing API tests](https://github.com/woocommerce/woocommerce/tree/trunk/plugins/woocommerce/tests/api-core-tests#guide-for-writing-api-tests).
+  - [Writing E2E tests](https://github.com/woocommerce/woocommerce/tree/trunk/plugins/woocommerce/tests/e2e-pw#guide-for-writing-e2e-tests).
 - Ensure you use LF line endings in your code editor. Use [EditorConfig](http://editorconfig.org/) if your editor supports it so that indentation, line endings and other settings are auto configured.
 - When committing, reference your issue number (#1234) and include a note about the fix.
 - Ensure that your code supports the minimum supported versions of PHP and WordPress; this is shown at the top of the `readme.txt` file.

plugins/woocommerce/changelog/add-instructions-for-testing-contribution

@@ -0,0 +1,5 @@
+Significance: patch
+Type: dev
+Comment: Update CONTRIBUTING.md file to include instructions on how adding unit, API and E2E tests when applicable.
+
+

plugins/woocommerce/tests/README.md

@@ -9,10 +9,10 @@ This document discusses unit tests. See [the e2e README](https://github.com/wooc
   - [Initial Setup](#initial-setup)
     - [MySQL database](#mysql-database)
     - [Setup instructions](#setup-instructions)
-  - [Running Tests](#running-tests)
+  - [Running Unit Tests](#running-unit-tests)
     - [Troubleshooting](#troubleshooting)
     - [Running tests in PHP 8](#running-tests-in-php-8)
-  - [Writing Tests](#writing-tests)
+  - [Guide for Writing Unit Tests](#guide-for-writing-unit-tests)
   - [Automated Tests](#automated-tests)
   - [Code Coverage](#code-coverage)
 
@@ -51,7 +51,7 @@ Example:
 
 **Important**: The `<db-name>` database will be created if it doesn't exist and all data will be removed during testing.
 
-## Running Tests
+## Running Unit Tests
 
 Change to the plugin root directory and type:
 
@@ -97,7 +97,7 @@ $ tests/bin/install.sh woocommerce_tests_1 root root
 
 Note that `woocommerce_tests` changed to `woocommerce_tests_1` as the `woocommerce_tests` database already exists due to the prior command.
 
-## Writing Tests
+## Guide for Writing Unit Tests
 
 There are three different unit test directories:
 

plugins/woocommerce/tests/api-core-tests/README.md

@@ -8,7 +8,7 @@ This package contains automated API tests for WooCommerce, based on Playwright a
 - [Introduction](#introduction)
 - [About the Environment](#about-the-environment)
 - [Test Variables](#test-variables)
-- [Guide for writing tests](#guide-for-writing-tests)
+- [Guide for writing API tests](#guide-for-writing-api-tests)
   - [What aspects of the API should we test?](#what-aspects-of-the-api-should-we-test)
   - [Creating test structure](#creating-test-structure)
   - [Test Data Setup/Teardown](#test-data-setupteardown)
@@ -130,7 +130,7 @@ After you run a test, it's best to restart the environment to start from a fresh
 - `pnpm env:destroy` when you make changes to `.wp-env.json`
 - `pnpm env:test` to spin up the test environment
 
-## Guide for writing tests
+## Guide for writing API tests
 
 When writing new tests, a good source on how to get started is to reference the [existing tests](https://github.com/woocommerce/woocommerce/tree/trunk/plugins/woocommerce/tests/api-core-tests/tests). Data that is required for the tests should be located in an equivalent file in the [data](https://github.com/woocommerce/woocommerce/tree/trunk/plugins/woocommerce/tests/api-core-tests/data) folder.