Validating GraphQL responses with testsfor Drupal 8 , 9 , 10 , and 11

Building on our previous lessons where we explored API testing using Postman and cURL and functional tests for REST/JSON:API, this lesson focuses on testing GraphQL responses in your headless Drupal application. Employing a robust testing strategy for GraphQL ensures your APIs deliver accurate and reliable data to your frontend applications.

Why Validate GraphQL Responses?

GraphQL is a query language for APIs, enabling clients to request specific data structures from the server. In headless Drupal setups, verifying GraphQL responses is crucial as:

• It ensures data returned matches the request, maintaining frontend integration integrity.
• It helps catch potential breakages in schema or data structures during development.
• It provides a safety net when introducing schema modifications.

Setting Up for Testing GraphQL in Drupal

Similar to REST/JSON:API, GraphQL testing involves simulating queries and ensuring the received responses align with expectations. Here's how to set up testing with PHPUnit and the GraphQL module in Drupal:

Step 1: Install Required Modules

If not already installed, ensure the GraphQL module is enabled in your Drupal environment. Use Composer if needed:

composer require drupal/graphql
drush en graphql

Step 2: Create a GraphQL Test Case

Create a directory structure in your module to house the test cases. Navigate to your custom module and create a test file:

cd modules/custom/your_module/tests/src/GraphQL
touch GraphQLQueryTest.php

Then, define a new test case by extending KernelTestBase, designed to test code under the kernel environment.

namespace Drupal\Tests\your_module\Kernel;

use Drupal\KernelTests\KernelTestBase;

/**
 * Tests the GraphQL queries.
 *
 * @group your_module
 */
class GraphQLQueryTest extends KernelTestBase {

  /**
   * {@inheritdoc}
   */
  protected static $modules = ['graphql', 'your_module'];

  /**
   * Tests a sample GraphQL query.
   */
  public function testArticleQuery() {
    // Craft the GraphQL query.
    $query = <<<'GRAPHQL'
{
  nodeById(id: "1") {
    title
    body {
      value
    }
  }
}
GRAPHQL;

    // Execute the query and validate the response.
    $response = $this->container->get('graphql.query_processor')->processQuery($query);
    $data = json_decode($response->getContent(), TRUE);

    // Assertions to verify expected structure and data.
    $this->assertEquals('Expected Article Title', $data['data']['nodeById']['title']);
    $this->assertNotEmpty($data['data']['nodeById']['body']['value']);
  }
}
    

Step 3: Run Your GraphQL Test

With the test case defined, execute your test suite to validate the GraphQL setup by running:

./vendor/bin/phpunit modules/custom/your_module/tests/src/GraphQL

This action will execute your tests, verifying the integrity of your GraphQL API responses.

Best Practices for GraphQL Testing

• Ensure your tests reflect different scenarios, including edge cases, to robustly evaluate API behavior.
• Strive to cover both expected and unexpected data structures in queries.
• Maintain clarity in your test cases to serve as documentation for other developers.

Conclusion and What’s Next?

By integrating tests for your GraphQL APIs, you create a safer development environment, facilitating faster problem identification and resolution. This approach ensures your Drupal application can deliver consistent data responses, vital for the reliability of your headless setup.

In the next lesson, we'll focus on Testing API Performance Under Load, where we'll delve into performance testing strategies to ensure your APIs can handle high traffic scenarios efficiently. Stay tuned!