drupal-kernel-test

Drupal Kernel Test

What It Is

A Kernel test partially boots the Drupal kernel: service container, database (SQLite by default), entity system, configuration and hooks. There is NO web server or browser.

Speed: 1-10 seconds per test (vs 10-120s for Functional).

This is the default test for custom modules. If in doubt between Kernel and Functional, choose Kernel. Only upgrade to Functional when you need to verify rendered HTML output.

When to Use

• Custom services that use entity storage, database, config, or the container
• Entity CRUD (create, read, update, delete)
• Database queries (entity queries, select queries)
• Access logic and permissions (without verifying UI)
• Plugin managers with real discovery
• Event subscribers
• Hook implementations
• Token replacement
• Migrations (migrate API)
• Field types, formatters, widgets (logic, not rendering)
• Form submit/validate handlers (handler logic, not the rendered form)
• Queue workers
• Cron hooks

When NOT to Use

• Need to verify rendered HTML -> Functional
• Need to submit forms via UI -> Functional
• Need JavaScript -> FunctionalJavascript
• Pure PHP logic without Drupal dependencies -> Unit

Base Template

<?php
declare(strict_types=1);

namespace Drupal\Tests\MODULE\Kernel;

use Drupal\KernelTests\KernelTestBase;

/**
 * Tests DESCRIPTION.
 *
 * @group MODULE
 */
class NameTest extends KernelTestBase {

  /**
   * Required modules. List dependencies BEFORE the module under test
   * (modules install in array order). Only the strictly necessary ones --
   * each extra module slows things down.
   */
  protected static $modules = [
    'system',
    'user',
    // dependencies...
    'MODULE',
  ];

  protected function setUp(): void {
    parent::setUp();
    $this->installEntitySchema('user');
    $this->installConfig(['system', 'MODULE']);
  }

  public function testSomething(): void {
    $service = $this->container->get('MODULE.my_service');
    // assertions...
  }

}

Setup Methods -- What to Use for What