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Gander Performance Testing

When to Use

Write Gander performance tests for modules with site-wide performance impact: event subscribers that fire on every request, cache invalidation logic, bulk operations, or features that execute complex queries.

Decision

Module Type Use Gander Why
Event-driven modules (ECA, Rules) Yes Event cascades can cause performance issues
Page request processors Yes Affects every page load
Mass operations (imports, bulk updates) Yes Query count and cache impact matter
Cache invalidation logic Yes Wrong invalidation destroys performance
Simple CRUD operations No Standard database operations
Admin-only features Maybe Low usage frequency, less critical

Pattern

<?php
namespace Drupal\Tests\my_module\FunctionalJavascript;

use Drupal\FunctionalJavascriptTests\PerformanceTestBase;
use PHPUnit\Framework\Attributes\Group;
use PHPUnit\Framework\Attributes\RequiresPhpExtension;
use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;

/**
 * Tests the my_module performance characteristics.
 */
#[Group('my_module')]
#[Group('Performance')]
#[Group('#slow')]
#[RequiresPhpExtension('apcu')]
#[RunTestsInSeparateProcesses]
class MyModulePerformanceTest extends PerformanceTestBase {

  protected static $modules = ['my_module', 'node'];
  protected $defaultTheme = 'stark';
  protected $profile = 'minimal';

  public function testFrontPagePerformanceImpact(): void {
    // Measure cold cache performance
    $performance_data = $this->collectPerformanceData(function() {
      $this->drupalGet('<front>');
    }, 'frontPageColdCache');

    // Set performance expectations
    $expected = [
      'queryCount' => 50,           // Maximum database queries
      'cacheGetCount' => 20,        // Maximum cache reads
      'cacheSetCount' => 15,        // Maximum cache writes
      'cacheDeleteCount' => 0,      // No cache deletes on normal request
      'cacheTagChecksumCount' => 5, // Cache tag validations
    ];

    $this->assertSame(200, $performance_data->getStatusCode());
    $this->assertLessThanOrEqual($expected['queryCount'], $performance_data->getQueryCount());
    $this->assertLessThanOrEqual($expected['cacheGetCount'], $performance_data->getCacheGetCount());
  }

  public function testHotCachePerformance(): void {
    // Warm cache
    $this->drupalGet('<front>');
    sleep(1);

    // Measure hot cache performance
    $performance_data = $this->collectPerformanceData(function() {
      $this->drupalGet('<front>');
    }, 'frontPageHotCache');

    // Expect minimal queries with warm cache
    $this->assertLessThanOrEqual(10, $performance_data->getQueryCount());
    $this->assertGreaterThan(5, $performance_data->getCacheGetCount());
  }

  public function testBulkOperationPerformance(): void {
    // Create test content
    $this->createNode(['type' => 'article', 'title' => 'Test']);

    // Measure bulk processing
    $performance_data = $this->collectPerformanceData(function() {
      $service = \Drupal::service('my_module.bulk_processor');

      // Process 100 items
      for ($i = 0; $i < 100; $i++) {
        $service->processItem(['id' => $i, 'data' => "test_$i"]);
      }
    }, 'bulkProcessing100Items');

    // Assert reasonable performance bounds
    $this->assertLessThanOrEqual(200, $performance_data->getQueryCount());
    $this->assertLessThanOrEqual(50, $performance_data->getCacheSetCount());

    // Ensure we're not invalidating too many caches
    $this->assertLessThanOrEqual(10, $performance_data->getCacheTagInvalidationCount());
  }
}

File Location: modules/my_module/tests/src/FunctionalJavascript/MyModulePerformanceTest.php

Note: Performance tests extend PerformanceTestBase (since Drupal 10.2) and use OpenTelemetry tracing.

Common Mistakes

  • Running performance tests without APCu enabled → Inaccurate cache metrics
  • Not warming caches before hot cache tests → Measuring cold cache instead
  • Setting unrealistic performance budgets → Tests always fail
  • Testing performance too early in development → Budgets change as features evolve
  • Not comparing with/without module enabled → Unknown actual impact

WHY these are mistakes: Performance tests measure real system behavior, which requires production-like conditions. APCu provides accurate cache metrics. Cache warming is required for realistic hot-cache measurements. Performance budgets must be based on actual measurements, not guesses. Always measure baseline performance without your module to understand true impact.

See Also