Skip to content

Kernel Tests with KernelTestBase

When to Use

Testing services, entities, database operations, and other Drupal integrations without HTTP overhead. Sweet spot for most Drupal testing.

Decision

Feature Unit Kernel Browser
Container & services No Yes Yes
Database access No Yes Yes
Entity API No Yes Yes
Config system No Yes Yes
HTTP requests No No Yes
Form rendering/submission No No Yes
Speed (seconds per test) 0.01 0.5-2 10-30

Use Kernel when: Service interaction matters, database needed, no user simulation required.

Pattern

Basic kernel test setup: 

namespace Drupal\Tests\my_module\Kernel;

use Drupal\KernelTests\KernelTestBase;

class MyServiceTest extends KernelTestBase {

  protected static $modules = ['system', 'user', 'my_module'];

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

  public function testServiceMethod(): void {
    $service = $this->container->get('my_module.my_service');
    $result = $service->doSomething();
    $this->assertNotEmpty($result);
  }
}

Module installation hierarchy: 1. protected static $modules -- loads module services/hooks, no install process 2. installEntitySchema('entity_type') -- creates database tables for entity type 3. installConfig(['module']) -- imports YAML config from config/install 4. installSchema('module', ['table']) -- creates custom tables from hook_schema

File location: modules/my_module/tests/src/Kernel/MyServiceTest.php

Reference: /core/tests/Drupal/KernelTests/KernelTestBase.php lines 69-82

Common Mistakes

  • Forgetting installEntitySchema() before entity operations -- "Table 'node' doesn't exist"
  • Not declaring module dependencies in $modules -- services missing from container
  • Using HTTP methods like $this->drupalGet() -- kernel tests don't support HTTP (use BrowserTestBase)
  • Installing unnecessary modules -- slower tests (only install what you need)
  • Not calling parent::setUp() -- bootstrap incomplete, random failures

See Also