We all know that PHPunit testing framework has been added into Drupal 8. More than that SimpleTest in Drupal 8 is deprecated now. PHP unit testing also helps you to check you business logic So let's learn and discuss about, how to write the PHPUnit test for our requirement.

1. PHPUnit for Drupal 8

2. Contents:
• Why PHPUnit?
• Before writing PHPUnit Test Case?
• How to write a PHPUnit Test?
• Running PHPUnit tests.
• Integrate with PHPStorm.

3. Why PHPUnit?
• No need for Bootstrap.
• Time saving.
• Apt for Continuous Integration.

4. Before writing PHPUnit Test Case?
• File structure and namespace
• vendor/bin/phpunit -> core/phpunit.xml.dist
• PHPUnit Base Classes
• UnitTestCase - Provides a base class and helpers for
Drupal unit tests
• KernelTestBase - Base class for functional integration
tests
• BrowserTestBase - Provides a test case for functional
Drupal tests.
• JavascriptTestBase - Base class for testing browser
interaction implemented in JavaScript (PhantomJS).

5. How to write a PHPUnit Test?
• Hands on Demo

6. Running PHPUnit tests
• Run all unit tests:
• cd core
../vendor/bin/phpunit --testsuite=unit
• Run one specific test:
• cd core
../vendor/bin/phpunit <path_to_test>/DemoTest.php
• Run kernel test and browser tests
• cd core
cp phpunit.xml.dist phpunit.xml
• Fill in SIMPLETEST_DB, SIMPLETEST_BASE_URL,
BROWSERTEST_OUTPUT_DIRECTORY and the printerClass for debugging
in phpunit.xml

7. Integrate with PHPStorm
• Settings > Languages & Frameworks > PHP
• CLI Interpreter
• Settings > Languages & Frameworks > PHP > PHPUnit
• PHPUnit library
• Use composer autoloader
• Path to script - vendor/bin/phpunit
• Test Runner
• Default configuration file - core/phpunit.xml.dist