Testing Examples 

namespace Netresearch\RteCKEditorImage\Tests\Functional\Controller;

use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;

class SelectImageControllerTest extends FunctionalTestCase
{
    protected $testExtensionsToLoad = [
        'typo3conf/ext/rte_ckeditor_image'
    ];

    /**
     * @test
     */
    public function infoActionReturnsJsonForValidFile(): void
    {
        // Import test data
        $this->importDataSet(__DIR__ . '/Fixtures/sys_file.xml');

        // Create request
        $request = $this->createRequest('/typo3/rte/wizard/selectimage')
            ->withQueryParams([
                'action' => 'info',
                'fileId' => 1,
                'table' => 'sys_file'
            ]);

        // Execute
        $response = $this->executeFrontendRequest($request);

        // Assert
        self::assertEquals(200, $response->getStatusCode());

        $json = json_decode((string)$response->getBody(), true);
        self::assertArrayHasKey('uid', $json);
        self::assertArrayHasKey('url', $json);
        self::assertEquals(1, $json['uid']);
    }
}

namespace Netresearch\RteCKEditorImage\Tests\Unit\Database;

use Netresearch\RteCKEditorImage\Database\RteImagesDbHook;
use TYPO3\TestingFramework\Core\Unit\UnitTestCase;

class RteImagesDbHookTest extends UnitTestCase
{
    /**
     * @test
     */
    public function transformRteAddsAltAttributeIfMissing(): void
    {
        $hook = new RteImagesDbHook(/* dependencies */);

        $input = '<img src="/fileadmin/image.jpg" data-htmlarea-file-uid="123" />';
        $output = $hook->transform_rte($input, $rteHtmlParser);

        self::assertStringContainsString('alt=', $output);
    }
}

# Functional tests
./vendor/bin/phpunit -c Build/phpunit-functional.xml

# Unit tests
./vendor/bin/phpunit -c Build/phpunit-unit.xml