DescriptionTraitTest.php

<?php

namespace Drupal\Tests\examples\Kernel;

use Drupal\KernelTests\KernelTestBase;
use Drupal\examples_description_test\Controller\SampleExampleController;

/**
 * Test of the Description Trait.
 *
 * @group examples
 */
class DescriptionTraitTest extends KernelTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'examples',
        'examples_description_test',
    ];
    
    /**
     * Make sure that the trait finds the template file and renders it.
     */
    public function testTemplateFile() {
        $sample_controller = SampleExampleController::create($this->container);
        // We want to test ::getDescriptionTemplatePath(), which is a protected
        // method. Use a little of the Old Black Reflection Magic.
        $ref_get_path = new \ReflectionMethod($sample_controller, 'getDescriptionTemplatePath');
        $ref_get_path->setAccessible(TRUE);
        $this->assertFileExists($ref_get_path->invoke($sample_controller));
        // And get our render output.
        $render_array = $sample_controller->description();
        // We cast to string, since renderPlain() returns a markup object.
        $output = (string) $this->container
            ->get('renderer')
            ->renderPlain($render_array);
        // Did the template load?
        $this->assertStringContainsString('Template loaded!', $output);
        // Were the variables resolved correctly?
        $this->assertStringContainsString('Used in module: examples_description_test.', $output);
        $this->assertStringContainsString('Our slogan for today: We aim to please.', $output);
    }

}