diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2059e50..edb342d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -120,7 +120,7 @@ jobs:
       - name: Run backend coverage
         run: |
           mkdir -p coverage
-          php -d pcov.directory=lib/Service vendor/bin/phpunit \
+          php -d pcov.directory=lib vendor/bin/phpunit \
             --configuration tests/phpunit.xml \
             --coverage-clover coverage/php-clover.xml \
             --coverage-text
diff --git a/codecov.yml b/codecov.yml
index 56f93dc..1cad411 100644
--- a/codecov.yml
+++ b/codecov.yml
@@ -15,9 +15,7 @@ ignore:
   - "js/**/*"
   - "tests/**/*"
   - "vendor/**/*"
-  - "lib/AppInfo/**/*"
   - "lib/Controller/**/*"
-  - "lib/Preview/**/*"
   - "src/main.ts"
   - "src/editor/editor-frame.ts"
   - "src/editor/editor-page.ts"
diff --git a/tests/Unit/AppInfo/ApplicationBootstrapTest.php b/tests/Unit/AppInfo/ApplicationBootstrapTest.php
new file mode 100644
index 0000000..1c2809b
--- /dev/null
+++ b/tests/Unit/AppInfo/ApplicationBootstrapTest.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\ExeLearning\Tests\Unit\AppInfo;
+
+use OCA\ExeLearning\AppInfo\Application;
+use OCA\ExeLearning\Preview\ElpxPreviewProvider;
+use OCP\AppFramework\Bootstrap\IBootContext;
+use OCP\AppFramework\Bootstrap\IRegistrationContext;
+use OCP\Util;
+use PHPUnit\Framework\TestCase;
+
+final class ApplicationBootstrapTest extends TestCase {
+	protected function setUp(): void {
+		Util::reset();
+	}
+
+	public function testRegistersThePreviewProvider(): void {
+		$context = $this->createMock(IRegistrationContext::class);
+		$context->expects(self::once())
+			->method('registerPreviewProvider')
+			->with(ElpxPreviewProvider::class, ElpxPreviewProvider::MIME_REGEX);
+
+		(new Application())->register($context);
+	}
+
+	public function testBootRegistersTheMainInitScript(): void {
+		$context = $this->createMock(IBootContext::class);
+
+		(new Application())->boot($context);
+
+		self::assertSame(
+			[[Application::APP_ID, 'exelearning-main']],
+			Util::$initScripts,
+		);
+	}
+}
diff --git a/tests/Unit/Preview/ElpxPreviewProviderTest.php b/tests/Unit/Preview/ElpxPreviewProviderTest.php
new file mode 100644
index 0000000..7f73404
--- /dev/null
+++ b/tests/Unit/Preview/ElpxPreviewProviderTest.php
@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\ExeLearning\Tests\Unit\Preview;
+
+use OCA\ExeLearning\Preview\ElpxPreviewProvider;
+use OCA\ExeLearning\Service\PermissionService;
+use OCA\ExeLearning\Service\ZipEntryService;
+use OCP\Files\File;
+use OCP\Files\FileInfo;
+use OCP\Image;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use RuntimeException;
+
+final class ElpxPreviewProviderTest extends TestCase {
+	private ZipEntryService $zipEntries;
+	private PermissionService $permissions;
+	private LoggerInterface $logger;
+	private ElpxPreviewProvider $provider;
+
+	protected function setUp(): void {
+		Image::$lastInstance = null;
+		Image::$validOverride = null;
+		$this->zipEntries = $this->createMock(ZipEntryService::class);
+		$this->permissions = $this->createMock(PermissionService::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->provider = new ElpxPreviewProvider(
+			$this->zipEntries,
+			$this->permissions,
+			$this->logger,
+		);
+	}
+
+	public function testReturnsTheRegisteredMimeRegex(): void {
+		self::assertSame(ElpxPreviewProvider::MIME_REGEX, $this->provider->getMimeType());
+	}
+
+	public function testDelegatesRealFilesToPermissionService(): void {
+		$file = $this->createMock(File::class);
+		$this->permissions->expects(self::once())
+			->method('isElpxFile')
+			->with($file)
+			->willReturn(true);
+
+		self::assertTrue($this->provider->isAvailable($file));
+	}
+
+	public function testFallbackFileInfoUsesSupportedExtensions(): void {
+		$elpx = $this->createMock(FileInfo::class);
+		$elpx->method('getName')->willReturn('Lesson.ELPX');
+		$legacy = $this->createMock(FileInfo::class);
+		$legacy->method('getName')->willReturn('Legacy.ElP');
+		$zip = $this->createMock(FileInfo::class);
+		$zip->method('getName')->willReturn('archive.zip');
+
+		self::assertTrue($this->provider->isAvailable($elpx));
+		self::assertTrue($this->provider->isAvailable($legacy));
+		self::assertFalse($this->provider->isAvailable($zip));
+	}
+
+	public function testBuildsThumbnailFromPackageScreenshot(): void {
+		$file = $this->createMock(File::class);
+		$this->zipEntries->expects(self::once())
+			->method('readEntry')
+			->with($file, 'screenshot.png')
+			->willReturn('valid-image-bytes');
+
+		$image = $this->provider->getThumbnail($file, 320, 180);
+
+		self::assertSame(Image::$lastInstance, $image);
+		self::assertSame('valid-image-bytes', Image::$lastInstance?->data);
+		self::assertSame([320, 180], Image::$lastInstance?->scaledTo);
+	}
+
+	public function testFallsBackWhenScreenshotIsMissingOrInvalid(): void {
+		$file = $this->createMock(File::class);
+		$this->zipEntries->expects(self::exactly(2))
+			->method('readEntry')
+			->willReturnOnConsecutiveCalls(null, 'invalid');
+
+		$missing = $this->provider->getThumbnail($file, 200, 100);
+		self::assertNotNull($missing);
+		self::assertSame([200, 100], Image::$lastInstance?->scaledTo);
+
+		$invalid = $this->provider->getThumbnail($file, 120, 80);
+		self::assertNotNull($invalid);
+		self::assertSame([120, 80], Image::$lastInstance?->scaledTo);
+	}
+
+	public function testReturnsNullWhenFallbackImageIsInvalid(): void {
+		$file = $this->createMock(File::class);
+		$this->zipEntries->method('readEntry')->willReturn(null);
+		Image::$validOverride = false;
+
+		self::assertNull($this->provider->getThumbnail($file, 100, 100));
+	}
+
+	public function testLogsPackageReadErrorsAndUsesFallback(): void {
+		$file = $this->createMock(File::class);
+		$file->method('getName')->willReturn('broken.elpx');
+		$error = new RuntimeException('broken archive');
+		$this->zipEntries->method('readEntry')->willThrowException($error);
+		$this->logger->expects(self::once())
+			->method('debug')
+			->with(
+				'eXeLearning preview failed',
+				self::callback(static function (array $context) use ($error): bool {
+					return ($context['app'] ?? null) === 'exelearning'
+						&& ($context['exception'] ?? null) === $error
+						&& ($context['file'] ?? null) === 'broken.elpx';
+				}),
+			);
+
+		self::assertNotNull($this->provider->getThumbnail($file, 64, 64));
+	}
+
+	public function testLegacyCroppedThumbnailApiReturnsNull(): void {
+		$file = $this->createMock(File::class);
+
+		self::assertNull($this->provider->getCroppedThumbnail($file, 100, 100, true));
+	}
+}
diff --git a/tests/bootstrap-standalone.php b/tests/bootstrap-standalone.php
index c4a1623..66f50f5 100644
--- a/tests/bootstrap-standalone.php
+++ b/tests/bootstrap-standalone.php
@@ -33,7 +33,9 @@ public function __construct(string $appName, array $urlParams = []) {}
 if (!interface_exists('OCP\\AppFramework\\Bootstrap\\IBootstrap', false)) {
 	eval('
 		namespace OCP\\AppFramework\\Bootstrap;
-		interface IRegistrationContext {}
+		interface IRegistrationContext {
+			public function registerPreviewProvider(string $class, string $mimeType): void;
+		}
 		interface IBootContext { public function getServerContainer(); public function getAppContainer(); }
 		interface IBootstrap {
 			public function register(IRegistrationContext $context): void;
@@ -44,11 +46,18 @@ public function boot(IBootContext $context): void;
 if (!interface_exists('OCP\\IPreview', false)) {
 	eval('namespace OCP; interface IPreview {}');
 }
-if (!interface_exists('OCP\\Files\\Node', false)) {
+if (!interface_exists('OCP\\Files\\FileInfo', false)) {
 	eval('
 		namespace OCP\\Files;
-		interface Node {
+		interface FileInfo {
 			public function getName();
+		}
+	');
+}
+if (!interface_exists('OCP\\Files\\Node', false)) {
+	eval('
+		namespace OCP\\Files;
+		interface Node extends FileInfo {
 			public function getMimeType();
 			public function getPermissions();
 		}
@@ -94,6 +103,55 @@ public function getUserFolder($userId);
 if (!class_exists('OCP\\Constants', false)) {
 	eval('namespace OCP; class Constants { public const PERMISSION_READ = 1; }');
 }
+if (!interface_exists('OCP\\IImage', false)) {
+	eval('namespace OCP; interface IImage {}');
+}
+if (!class_exists('OCP\\Image', false)) {
+	eval('
+		namespace OCP;
+		class Image implements IImage {
+			public static ?self $lastInstance = null;
+			public static ?bool $validOverride = null;
+			public string $data = "";
+			public ?array $scaledTo = null;
+			public function __construct() { self::$lastInstance = $this; }
+			public function loadFromData(string $data): void { $this->data = $data; }
+			public function valid(): bool { return self::$validOverride ?? ($this->data !== "" && $this->data !== "invalid"); }
+			public function scaleDownToFit(int $maxX, int $maxY): void { $this->scaledTo = [$maxX, $maxY]; }
+		}
+	');
+}
+if (!interface_exists('OCP\\Preview\\IProviderV2', false)) {
+	eval('namespace OCP\\Preview; interface IProviderV2 {}');
+}
+if (!interface_exists('OCP\\Files\\SimpleFS\\ISimpleFile', false)) {
+	eval('namespace OCP\\Files\\SimpleFS; interface ISimpleFile {}');
+}
+if (!interface_exists('Psr\\Log\\LoggerInterface', false)) {
+	eval('
+		namespace Psr\\Log;
+		interface LoggerInterface {
+			public function emergency(string|\\Stringable $message, array $context = []): void;
+			public function alert(string|\\Stringable $message, array $context = []): void;
+			public function critical(string|\\Stringable $message, array $context = []): void;
+			public function error(string|\\Stringable $message, array $context = []): void;
+			public function warning(string|\\Stringable $message, array $context = []): void;
+			public function notice(string|\\Stringable $message, array $context = []): void;
+			public function info(string|\\Stringable $message, array $context = []): void;
+			public function debug(string|\\Stringable $message, array $context = []): void;
+			public function log($level, string|\\Stringable $message, array $context = []): void;
+		}
+	');
+}
 if (!class_exists('OCP\\Util', false)) {
-	eval('namespace OCP; class Util { public static function addInitScript(string $app, string $script): void {} public static function addScript(string $app, string $script): void {} }');
+	eval('
+		namespace OCP;
+		class Util {
+			public static array $initScripts = [];
+			public static array $scripts = [];
+			public static function addInitScript(string $app, string $script): void { self::$initScripts[] = [$app, $script]; }
+			public static function addScript(string $app, string $script): void { self::$scripts[] = [$app, $script]; }
+			public static function reset(): void { self::$initScripts = []; self::$scripts = []; }
+		}
+	');
 }
diff --git a/tests/phpunit.xml b/tests/phpunit.xml
index 82661ec..70dcf75 100644
--- a/tests/phpunit.xml
+++ b/tests/phpunit.xml
@@ -14,6 +14,8 @@
     </testsuites>
     <source>
         <include>
+            <directory>../lib/AppInfo</directory>
+            <directory>../lib/Preview</directory>
             <directory>../lib/Service</directory>
         </include>
     </source>