diff --git a/apps/theming/tests/Controller/ThemingControllerTest.php b/apps/theming/tests/Controller/ThemingControllerTest.php
index b9c291c957..9f6b41cb50 100644
--- a/apps/theming/tests/Controller/ThemingControllerTest.php
+++ b/apps/theming/tests/Controller/ThemingControllerTest.php
@@ -49,12 +49,12 @@ use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\Files\IAppData;
 use OCP\Files\NotFoundException;
 use OCP\Files\SimpleFS\ISimpleFile;
-use OCP\Files\SimpleFS\ISimpleFolder;
 use OCP\IConfig;
 use OCP\IL10N;
 use OCP\IRequest;
 use OCP\ITempManager;
 use OCP\IURLGenerator;
+use PHPUnit\Framework\MockObject\MockObject;
 use Test\TestCase;
 
 class ThemingControllerTest extends TestCase {
@@ -98,12 +98,12 @@ class ThemingControllerTest extends TestCase {
 		$this->urlGenerator = $this->createMock(IURLGenerator::class);
 		$this->imageManager = $this->createMock(ImageManager::class);
 
-		$this->timeFactory = $this->createMock(ITimeFactory::class);
-		$this->timeFactory->expects($this->any())
+		$timeFactory = $this->createMock(ITimeFactory::class);
+		$timeFactory->expects($this->any())
 			->method('getTime')
 			->willReturn(123);
 
-		$this->overwriteService(ITimeFactory::class, $this->timeFactory);
+		$this->overwriteService(ITimeFactory::class, $timeFactory);
 
 		$this->themingController = new ThemingController(
 			'theming',
@@ -293,12 +293,9 @@ class ThemingControllerTest extends TestCase {
 				return $str;
 			});
 
-		$folder = $this->createMock(ISimpleFolder::class);
-		$this->appData
-			->expects($this->once())
-			->method('getFolder')
-			->with('images')
-			->willReturn($folder);
+		$this->imageManager->expects($this->once())
+			->method('updateImage')
+			->willThrowException(new \Exception('Unsupported image type'));
 
 		$expected = new DataResponse(
 			[
@@ -337,12 +334,9 @@ class ThemingControllerTest extends TestCase {
 				return $str;
 			});
 
-		$folder = $this->createMock(ISimpleFolder::class);
-		$this->appData
-			->expects($this->once())
-			->method('getFolder')
-			->with('images')
-			->willReturn($folder);
+		$this->imageManager->expects($this->once())
+			->method('updateImage')
+			->willThrowException(new \Exception('Unsupported image type'));
 
 		$expected = new DataResponse(
 			[
@@ -398,31 +392,6 @@ class ThemingControllerTest extends TestCase {
 				return $str;
 			});
 
-
-		$file = $this->createMock(ISimpleFile::class);
-		$folder = $this->createMock(ISimpleFolder::class);
-		if ($folderExists) {
-			$this->appData
-				->expects($this->once())
-				->method('getFolder')
-				->with('images')
-				->willReturn($folder);
-		} else {
-			$this->appData
-				->expects($this->at(0))
-				->method('getFolder')
-				->with('images')
-				->willThrowException(new NotFoundException());
-			$this->appData
-				->expects($this->at(1))
-				->method('newFolder')
-				->with('images')
-				->willReturn($folder);
-		}
-		$folder->expects($this->once())
-			->method('newFile')
-			->with('logo')
-			->willReturn($file);
 		$this->urlGenerator->expects($this->once())
 			->method('linkTo')
 			->willReturn('serverCss');
@@ -430,6 +399,10 @@ class ThemingControllerTest extends TestCase {
 			->method('getImageUrl')
 			->with('logo')
 			->willReturn('imageUrl');
+
+		$this->imageManager->expects($this->once())
+			->method('updateImage');
+
 		$expected = new DataResponse(
 			[
 				'data' =>
@@ -474,30 +447,8 @@ class ThemingControllerTest extends TestCase {
 				return $str;
 			});
 
-		$file = $this->createMock(ISimpleFile::class);
-		$folder = $this->createMock(ISimpleFolder::class);
-		if ($folderExists) {
-			$this->appData
-				->expects($this->once())
-				->method('getFolder')
-				->with('images')
-				->willReturn($folder);
-		} else {
-			$this->appData
-				->expects($this->at(0))
-				->method('getFolder')
-				->with('images')
-				->willThrowException(new NotFoundException());
-			$this->appData
-				->expects($this->at(1))
-				->method('newFolder')
-				->with('images')
-				->willReturn($folder);
-		}
-		$folder->expects($this->once())
-			->method('newFile')
-			->with('background')
-			->willReturn($file);
+		$this->imageManager->expects($this->once())
+			->method('updateImage');
 
 		$this->urlGenerator->expects($this->once())
 			->method('linkTo')
@@ -548,12 +499,9 @@ class ThemingControllerTest extends TestCase {
 				return $str;
 			});
 
-		$folder = $this->createMock(ISimpleFolder::class);
-		$this->appData
-			->expects($this->once())
-			->method('getFolder')
-			->with('images')
-			->willReturn($folder);
+		$this->imageManager->expects($this->once())
+			->method('updateImage')
+			->willThrowException(new \Exception('Unsupported image type'));
 
 		$expected = new DataResponse(
 			[
@@ -723,9 +671,6 @@ class ThemingControllerTest extends TestCase {
 			->method('linkTo')
 			->with('', '/core/css/someHash-css-variables.scss')
 			->willReturn('/nextcloudWebroot/core/css/someHash-css-variables.scss');
-		$this->imageManager->expects($this->once())
-			->method('delete')
-			->with($filename);
 
 		$expected = new DataResponse(
 			[
diff --git a/apps/theming/tests/ImageManagerTest.php b/apps/theming/tests/ImageManagerTest.php
index 1187ecf036..c62b51d733 100644
--- a/apps/theming/tests/ImageManagerTest.php
+++ b/apps/theming/tests/ImageManagerTest.php
@@ -35,7 +35,9 @@ use OCP\Files\SimpleFS\ISimpleFolder;
 use OCP\ICacheFactory;
 use OCP\IConfig;
 use OCP\ILogger;
+use OCP\ITempManager;
 use OCP\IURLGenerator;
+use PHPUnit\Framework\MockObject\MockObject;
 use Test\TestCase;
 
 class ImageManagerTest extends TestCase {
@@ -52,6 +54,8 @@ class ImageManagerTest extends TestCase {
 	private $cacheFactory;
 	/** @var ILogger|\PHPUnit_Framework_MockObject_MockObject */
 	private $logger;
+	/** @var ITempManager|MockObject */
+	private $tempManager;
 
 	protected function setUp(): void {
 		parent::setUp();
@@ -60,12 +64,14 @@ class ImageManagerTest extends TestCase {
 		$this->urlGenerator = $this->createMock(IURLGenerator::class);
 		$this->cacheFactory = $this->createMock(ICacheFactory::class);
 		$this->logger = $this->createMock(ILogger::class);
+		$this->tempManager = $this->createMock(ITempManager::class);
 		$this->imageManager = new ImageManager(
 			$this->config,
 			$this->appData,
 			$this->urlGenerator,
 			$this->cacheFactory,
-			$this->logger
+			$this->logger,
+			$this->tempManager
 		);
 	}
 
@@ -326,4 +332,56 @@ class ImageManagerTest extends TestCase {
 			->willReturn($folders[2]);
 		$this->imageManager->cleanup();
 	}
+
+
+	public function dataUpdateImage() {
+		return [
+			['background', __DIR__ . '/../../../tests/data/testimage.png', true, true],
+			['background', __DIR__ . '/../../../tests/data/testimage.png', false, true],
+			['background', __DIR__ . '/../../../tests/data/testimage.jpg', true, true],
+			['logo', __DIR__ . '/../../../tests/data/testimagelarge.svg', true, false],
+		];
+	}
+
+	/**
+	 * @dataProvider dataUpdateImage
+	 */
+	public function testUpdateImage($key, $tmpFile, $folderExists, $shouldConvert) {
+		$file = $this->createMock(ISimpleFile::class);
+		$folder = $this->createMock(ISimpleFolder::class);
+		$oldFile = $this->createMock(ISimpleFile::class);
+		$folder->expects($this->any())
+			->method('getFile')
+			->willReturn($oldFile);
+		if ($folderExists) {
+			$this->appData
+				->expects($this->any())
+				->method('getFolder')
+				->with('images')
+				->willReturn($folder);
+		} else {
+			$this->appData
+				->expects($this->any())
+				->method('getFolder')
+				->with('images')
+				->willThrowException(new NotFoundException());
+			$this->appData
+				->expects($this->any())
+				->method('newFolder')
+				->with('images')
+				->willReturn($folder);
+		}
+		$folder->expects($this->once())
+			->method('newFile')
+			->with($key)
+			->willReturn($file);
+
+		if ($shouldConvert) {
+			$this->tempManager->expects($this->once())
+				->method('getTemporaryFile')
+				->willReturn('/tmp/randomtempfile-theming');
+		}
+
+		$this->imageManager->updateImage($key, $tmpFile);
+	}
 }