diff --git a/tests/Core/FormTest.php b/tests/Core/FormTest.php
index 938a6bf2dd..06279958a6 100644
--- a/tests/Core/FormTest.php
+++ b/tests/Core/FormTest.php
@@ -24,8 +24,10 @@ namespace App\Tests\Core;
 use App\Core\DB\DB;
 use App\Core\Form;
 use App\Entity\GSActor;
+use App\Util\Exception\ServerException;
 use App\Util\Form\ArrayTransformer;
 use App\Util\GNUsocialTestCase;
+use Jchook\AssertThrows\AssertThrows;
 use Symfony\Component\Form\Extension\Core\Type\SubmitType;
 use Symfony\Component\Form\Extension\Core\Type\TextareaType;
 use Symfony\Component\Form\Form as SymfForm;
@@ -33,13 +35,15 @@ use Symfony\Component\HttpFoundation\Request;
 
 class FormTest extends GNUsocialTestCase
 {
+    use AssertThrows;
+
     public function testCreate()
     {
         parent::bootKernel();
         $form = Form::create($form_array = [
             ['content',     TextareaType::class, ['label' => ' ', 'data' => '', 'attr' => ['placeholder' => 'placeholder']]],
             ['array_trans', TextareaType::class, ['data' => ['foo', 'bar'], 'transformer' => ArrayTransformer::class]],
-            ['testpost',        SubmitType::class,   ['label' => 'Post']],
+            ['testpost',    SubmitType::class,   ['label' => 'Post']],
         ]);
         static::assertSame(get_class($form), 'Symfony\\Component\\Form\\Form');
         foreach ($form as $name => $f) {
@@ -74,6 +78,15 @@ class FormTest extends GNUsocialTestCase
         static::assertTrue(Form::isRequired($form_array, 'content'));
     }
 
+    /**
+     * Using 'save' or 'submit' as a form name is not allowed, becuase then they're likely to
+     * collide with other forms in the same page
+     */
+    public function testDisallowedGenericFormName()
+    {
+        static::assertThrows(ServerException::class, fn () => Form::create([['save', SubmitType::class, []]]));
+    }
+
     /**
      * Test creating a form with default values pulled from an existing object. Can be used in conjunction with `Form::hanlde` to update said object
      */
diff --git a/tests/Entity/AttachmentTest.php b/tests/Entity/AttachmentTest.php
index 8d38bc38cf..beb58bc094 100644
--- a/tests/Entity/AttachmentTest.php
+++ b/tests/Entity/AttachmentTest.php
@@ -20,12 +20,14 @@
 namespace App\Tests\Entity;
 
 use App\Core\DB\DB;
+use App\Core\Event;
 use App\Core\GSFile;
 use App\Entity\AttachmentToNote;
 use App\Entity\Note;
 use App\Util\GNUsocialTestCase;
 use App\Util\TemporaryFile;
 use Jchook\AssertThrows\AssertThrows;
+use Symfony\Component\HttpFoundation\File\File;
 
 class AttachmentTest extends GNUsocialTestCase
 {
@@ -69,6 +71,26 @@ class AttachmentTest extends GNUsocialTestCase
         static::assertSame([], DB::findBy('attachment', ['filehash' => $hash]));
     }
 
+    public function testSanitizeAndStoreFileAsAttachment()
+    {
+        $test = function (string $method) {
+            $temp_file = new TemporaryFile();
+            $temp_file->write(file_get_contents(INSTALLDIR . '/tests/sample-uploads/gnu-logo.png'));
+            Event::handle('HashFile', [$temp_file->getPathname(), &$hash]);
+            $attachment = DB::findOneBy('attachment', ['filehash' => $hash]);
+            $attachment->{$method}();
+            DB::flush();
+
+            $file = new File($temp_file->getRealPath());
+            GSFile::sanitizeAndStoreFileAsAttachment($file);
+            static::assertNotNull($attachment->getFilename());
+            static::assertTrue(file_exists($attachment->getPath()));
+        };
+
+        $test('deleteStorage');
+        $test('kill');
+    }
+
     public function testGetBestTitle()
     {
         $attachment = DB::findBy('attachment', ['mimetype' => 'image/png'], limit: 1)[0];
@@ -92,4 +114,20 @@ class AttachmentTest extends GNUsocialTestCase
         $id         = $attachment->getId();
         static::assertSame("/attachment/{$id}/view", $attachment->getUrl());
     }
+
+    public function testMimetype()
+    {
+        $file = new \SplFileInfo(INSTALLDIR . '/tests/sample-uploads/image.jpg');
+        Event::handle('HashFile', [$file->getPathname(), &$hash]);
+        $attachment = DB::findOneBy('attachment', ['filehash' => $hash]);
+
+        static::assertSame('image', $attachment->getMimetypeMajor());
+        static::assertSame('jpeg', $attachment->getMimetypeMinor());
+
+        $mimetype = $attachment->getMimetype();
+        $attachment->setMimetype(null);
+        static::assertNull($attachment->getMimetypeMajor());
+        static::assertNull($attachment->getMimetypeMinor());
+        $attachment->setMimetype($mimetype);
+    }
 }
diff --git a/tests/Entity/AttachmentThumbnailTest.php b/tests/Entity/AttachmentThumbnailTest.php
index ab2c624f69..eb03fe7d11 100644
--- a/tests/Entity/AttachmentThumbnailTest.php
+++ b/tests/Entity/AttachmentThumbnailTest.php
@@ -22,6 +22,7 @@ namespace App\Tests\Entity;
 use App\Core\DB\DB;
 use App\Core\Event;
 use App\Entity\AttachmentThumbnail;
+use App\Util\Exception\ClientException;
 use App\Util\Exception\NotStoredLocallyException;
 use App\Util\GNUsocialTestCase;
 use Functional as F;
@@ -67,6 +68,17 @@ class AttachmentThumbnailTest extends GNUsocialTestCase
         $attachment->kill();
     }
 
+    public function testInvalidThumbnail()
+    {
+        parent::bootKernel();
+
+        $file = new \SplFileInfo(INSTALLDIR . '/tests/sample-uploads/spreadsheet.ods');
+        Event::handle('HashFile', [$file->getPathname(), &$hash]);
+        $attachment = DB::findOneBy('attachment', ['filehash' => $hash]);
+
+        static::assertThrows(ClientException::class, fn () => AttachmentThumbnail::getOrCreate($attachment, width: 1, height: 1, crop: false));
+    }
+
     public function testPredictScalingValues()
     {
         // Test without cropping
diff --git a/tests/sample-uploads/gnu-logo.png b/tests/sample-uploads/gnu-logo.png
new file mode 100644
index 0000000000..5d79e748ef
Binary files /dev/null and b/tests/sample-uploads/gnu-logo.png differ