diff --git a/backend/tests/Feature/SetsEndpointTest.php b/backend/tests/Feature/SetsEndpointTest.php
index 8f4af23..54a730a 100644
--- a/backend/tests/Feature/SetsEndpointTest.php
+++ b/backend/tests/Feature/SetsEndpointTest.php
@@ -140,6 +140,88 @@ class SetsEndpointTest extends TestCase
         );
     }
 
+    public function testUpdateSetRequiresAuthentication(): void
+    {
+        $setRepository = app(SetRepository::class);
+        $set = $setRepository->create(new CreateSetDto(
+            name: 'Original Set',
+            description: 'Original set description',
+            iconImageUrl: '/assets/original-icon.png',
+        ));
+
+        $response = $this->postJson(
+            "/api/sets/{$set->getId()}/update",
+            [
+                'name' => 'Updated Set',
+                'description' => 'Updated set description',
+            ],
+        );
+
+        $response->assertUnauthorized();
+        $response->assertExactJson([
+            'error' => 'unauthenticated',
+        ]);
+    }
+
+    public function testAuthenticatedUpdateSetUpdatesMediaPayloadOnly(): void
+    {
+        $setRepository = app(SetRepository::class);
+        $elementRepository = app(ElementRepository::class);
+        $this->createSession('valid-token');
+        $set = $setRepository->create(new CreateSetDto(
+            name: 'Original Set',
+            description: 'Original set description',
+            iconImageUrl: '/assets/original-icon.png',
+        ));
+        $rootElement = $elementRepository->create(new CreateElementDto(
+            set: $set,
+            title: 'Original Root',
+            description: 'Original root description',
+            iconImageUrl: '/assets/original-icon.png',
+            richText: '',
+            shortPdfPath: null,
+            longPdfPath: null,
+            youtubeUrl: null,
+            parentElement: null,
+        ));
+
+        $response = $this->withCredentials()
+            ->withUnencryptedCookie('auth_token', 'valid-token')
+            ->postJson("/api/sets/{$set->getId()}/update", [
+                'name' => 'Updated Set',
+                'description' => 'Updated set description',
+            ]);
+
+        $response->assertOk();
+        $response->assertExactJson([
+            'set' => [
+                'id' => $set->getId(),
+                'name' => 'Updated Set',
+                'description' => 'Updated set description',
+                'iconImageUrl' => '/assets/original-icon.png',
+                'rootElementId' => $rootElement->getId(),
+            ],
+        ]);
+
+        $updatedSet = $setRepository->find($set->getId());
+        $this->assertNotNull($updatedSet);
+        $this->assertSame('Updated Set', $updatedSet->getName());
+        $this->assertSame(
+            'Updated set description',
+            $updatedSet->getDescription(),
+        );
+
+        $unchangedRootElement = $elementRepository->find(
+            $rootElement->getId(),
+        );
+        $this->assertNotNull($unchangedRootElement);
+        $this->assertSame('Original Root', $unchangedRootElement->getTitle());
+        $this->assertSame(
+            'Original root description',
+            $unchangedRootElement->getDescription(),
+        );
+    }
+
     public function testCreateSetRequiresIconImage(): void
     {
         $this->createSession('valid-token');
diff --git a/backend/tests/Unit/Set/UseCases/UpdateSetTest.php b/backend/tests/Unit/Set/UseCases/UpdateSetTest.php
new file mode 100644
index 0000000..a1bba41
--- /dev/null
+++ b/backend/tests/Unit/Set/UseCases/UpdateSetTest.php
@@ -0,0 +1,181 @@
+<?php
+
+namespace Tests\Unit\Set\UseCases;
+
+use App\Element\CreateElementDto;
+use App\Exceptions\BadRequestException;
+use App\Exceptions\NotFoundException;
+use App\Set\CreateSetDto;
+use App\Set\Set as DomainSet;
+use App\Set\UseCases\UpdateSet\UpdateSet;
+use App\Set\UseCases\UpdateSet\UpdateSetRequest;
+use Tests\Fakes\FakeElementRepository;
+use Tests\Fakes\FakeFilesystem;
+use Tests\Fakes\FakeSetRepository;
+use Tests\TestCase;
+
+class UpdateSetTest extends TestCase
+{
+    private FakeSetRepository $setRepository;
+
+    private FakeElementRepository $elementRepository;
+
+    private FakeFilesystem $filesystem;
+
+    private UpdateSet $updateSet;
+
+    protected function setUp(): void
+    {
+        $this->setRepository = new FakeSetRepository();
+        $this->elementRepository = new FakeElementRepository();
+        $this->filesystem = new FakeFilesystem();
+        $this->updateSet = new UpdateSet(
+            $this->setRepository,
+            $this->filesystem,
+        );
+    }
+
+    public function testUpdatesSetWithoutChangingRootElement(): void
+    {
+        $set = $this->setRepository->create(new CreateSetDto(
+            name: 'Original Set',
+            description: 'Original set description',
+            iconImageUrl: 'set-icons/original.png',
+        ));
+        $rootElement = $this->elementRepository->create(new CreateElementDto(
+            set: $set,
+            title: 'Original Root',
+            description: 'Original root description',
+            iconImageUrl: 'set-icons/original.png',
+            richText: '',
+            shortPdfPath: null,
+            longPdfPath: null,
+            youtubeUrl: null,
+            parentElement: null,
+        ));
+
+        $updatedSet = $this->updateSet->execute(new UpdateSetRequest(
+            id: $set->getId(),
+            name: 'Updated Set',
+            description: 'Updated set description',
+            iconImageContents: null,
+            iconImageOriginalName: null,
+            iconImageMimeType: null,
+            iconImageSizeBytes: null,
+        ));
+
+        $this->assertSame('Updated Set', $updatedSet->getName());
+        $this->assertSame(
+            'Updated set description',
+            $updatedSet->getDescription(),
+        );
+        $this->assertSame(
+            'set-icons/original.png',
+            $updatedSet->getIconImageUrl(),
+        );
+
+        $unchangedRootElement = $this->elementRepository->find(
+            $rootElement->getId(),
+        );
+        $this->assertNotNull($unchangedRootElement);
+        $this->assertSame('Original Root', $unchangedRootElement->getTitle());
+        $this->assertSame(
+            'Original root description',
+            $unchangedRootElement->getDescription(),
+        );
+        $this->assertSame(
+            'set-icons/original.png',
+            $unchangedRootElement->getIconImageUrl(),
+        );
+    }
+
+    public function testReplacesSetIconAndDeletesOldManagedIcon(): void
+    {
+        $set = $this->setRepository->create(new CreateSetDto(
+            name: 'Original Set',
+            description: 'Original set description',
+            iconImageUrl: 'set-icons/original.png',
+        ));
+
+        $updatedSet = $this->updateSet->execute(new UpdateSetRequest(
+            id: $set->getId(),
+            name: 'Updated Set',
+            description: 'Updated set description',
+            iconImageContents: 'image contents',
+            iconImageOriginalName: 'updated.png',
+            iconImageMimeType: 'image/png',
+            iconImageSizeBytes: 13,
+        ));
+
+        $this->assertSame(
+            'set-icons/fake-updated.png',
+            $updatedSet->getIconImageUrl(),
+        );
+        $this->assertCount(1, $this->filesystem->uploads);
+        $this->assertSame('set-icons', $this->filesystem->uploads[0]['folder']);
+        $this->assertSame([
+            'set-icons/original.png',
+        ], $this->filesystem->deletedPaths);
+    }
+
+    public function testRequiresName(): void
+    {
+        $set = $this->createSet();
+
+        $this->expectException(BadRequestException::class);
+        $this->expectExceptionMessage('name is required');
+
+        $this->updateSet->execute(new UpdateSetRequest(
+            id: $set->getId(),
+            name: '',
+            description: 'Updated set description',
+            iconImageContents: null,
+            iconImageOriginalName: null,
+            iconImageMimeType: null,
+            iconImageSizeBytes: null,
+        ));
+    }
+
+    public function testRequiresDescription(): void
+    {
+        $set = $this->createSet();
+
+        $this->expectException(BadRequestException::class);
+        $this->expectExceptionMessage('description is required');
+
+        $this->updateSet->execute(new UpdateSetRequest(
+            id: $set->getId(),
+            name: 'Updated Set',
+            description: '',
+            iconImageContents: null,
+            iconImageOriginalName: null,
+            iconImageMimeType: null,
+            iconImageSizeBytes: null,
+        ));
+    }
+
+    public function testThrowsWhenSetIsMissing(): void
+    {
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionMessage('Set not found');
+
+        $this->updateSet->execute(new UpdateSetRequest(
+            id: 999,
+            name: 'Updated Set',
+            description: 'Updated set description',
+            iconImageContents: null,
+            iconImageOriginalName: null,
+            iconImageMimeType: null,
+            iconImageSizeBytes: null,
+        ));
+    }
+
+    private function createSet(): DomainSet
+    {
+        return $this->setRepository->create(new CreateSetDto(
+            name: 'Original Set',
+            description: 'Original set description',
+            iconImageUrl: 'set-icons/original.png',
+        ));
+    }
+}