diff --git a/backend/tests/api/v1/documents/test_new_features.py b/backend/tests/api/v1/documents/test_new_features.py
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+++ b/backend/tests/api/v1/documents/test_new_features.py
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+"""
+Тесты для новых фич документооборота:
+- DocumentTag ViewSet
+- DocumentType ViewSet
+- Cabinet ViewSet
+- DocumentComment ViewSet
+- Related Documents
+- Thumbnails API
+- django-reversion endpoints (versions, activity, revert)
+"""
+
+import pytest
+from django.contrib.auth import get_user_model
+from django.urls import reverse
+from rest_framework import status
+from rest_framework.test import APIClient
+
+from documents.models import (
+    Document,
+    DocumentTag,
+    DocumentType,
+    Cabinet,
+    DocumentComment,
+)
+from filer.models import Folder, File as FilerFile
+from employees.models import Department
+
+User = get_user_model()
+
+
+@pytest.fixture
+def api_client():
+    return APIClient()
+
+
+@pytest.fixture
+def user(db):
+    """Обычный пользователь."""
+    return User.objects.create_user(
+        username='testuser',
+        email='test@example.com',
+        password='testpass123',
+        first_name='Test',
+        last_name='User'
+    )
+
+
+@pytest.fixture
+def staff_user(db):
+    """Staff пользователь."""
+    return User.objects.create_user(
+        username='staffuser',
+        email='staff@example.com',
+        password='staffpass123',
+        first_name='Staff',
+        last_name='User',
+        is_staff=True
+    )
+
+
+@pytest.fixture
+def document(user):
+    """Тестовый документ."""
+    return Document.objects.create(
+        title='Test Document',
+        description='Test Description',
+        uploaded_by=user,
+        status='draft'
+    )
+
+
+@pytest.fixture
+def document_tag(db):
+    """Тестовый тег."""
+    return DocumentTag.objects.create(
+        name='Important',
+        slug='important',
+        color='#ff0000'
+    )
+
+
+@pytest.fixture
+def document_type(db):
+    """Тестовый тип документа."""
+    return DocumentType.objects.create(
+        name='Contract',
+        code='contract',
+        description='Legal contracts',
+        is_active=True
+    )
+
+
+@pytest.fixture
+def cabinet(user):
+    """Тестовый кабинет."""
+    return Cabinet.objects.create(
+        name='Test Cabinet',
+        slug='test-cabinet',
+        description='Test Cabinet Description',
+        created_by=user
+    )
+
+
+# =============================================================================
+# DOCUMENTTAG VIEWSET TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestDocumentTagViewSet:
+    """Тесты для DocumentTagViewSet."""
+    
+    def test_list_tags(self, api_client, user, document_tag):
+        """Тест получения списка тегов."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:document-tags-list')
+        
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert len(response.data['results']) == 1
+        assert response.data['results'][0]['name'] == 'Important'
+    
+    def test_create_tag(self, api_client, user):
+        """Тест создания тега."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:document-tags-list')
+        
+        data = {
+            'name': 'Urgent',
+            'slug': 'urgent',
+            'color': '#00ff00'
+        }
+        response = api_client.post(url, data)
+        
+        assert response.status_code == status.HTTP_201_CREATED
+        assert DocumentTag.objects.filter(slug='urgent').exists()
+    
+    def test_tag_documents(self, api_client, user, document_tag, document):
+        """Тест получения документов тега."""
+        document_tag.documents.add(document)
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:document-tags-documents', args=[document_tag.pk])
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert len(response.data) == 1
+
+
+# =============================================================================
+# DOCUMENTTYPE VIEWSET TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestDocumentTypeViewSet:
+    """Тесты для DocumentTypeViewSet."""
+    
+    def test_list_types(self, api_client, user, document_type):
+        """Тест получения списка типов."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:document-types-list')
+        
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert len(response.data['results']) == 1
+        assert response.data['results'][0]['name'] == 'Contract'
+    
+    def test_filter_inactive(self, api_client, user, document_type):
+        """Тест фильтрации неактивных типов."""
+        DocumentType.objects.create(
+            name='Inactive Type',
+            code='inactive',
+            is_active=False
+        )
+        api_client.force_authenticate(user=user)
+        
+        # Без фильтра - только активные
+        url = reverse('v1:document-types-list')
+        response = api_client.get(url)
+        assert len(response.data['results']) == 1
+        
+        # С фильтром - все
+        response = api_client.get(url, {'include_inactive': 'true'})
+        assert len(response.data['results']) == 2
+
+
+# =============================================================================
+# CABINET VIEWSET TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestCabinetViewSet:
+    """Тесты для CabinetViewSet."""
+    
+    def test_list_cabinets(self, api_client, user, cabinet):
+        """Тест получения списка кабинетов."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:cabinets-list')
+        
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert len(response.data['results']) == 1
+    
+    def test_create_cabinet(self, api_client, user):
+        """Тест создания кабинета."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:cabinets-list')
+        
+        data = {
+            'name': 'New Cabinet',
+            'slug': 'new-cabinet',
+            'description': 'Test'
+        }
+        response = api_client.post(url, data)
+        
+        assert response.status_code == status.HTTP_201_CREATED
+        cabinet = Cabinet.objects.get(slug='new-cabinet')
+        assert cabinet.created_by == user
+    
+    def test_add_document_to_cabinet(self, api_client, user, cabinet, document):
+        """Тест добавления документа в кабинет."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:cabinets-add-document', args=[cabinet.pk])
+        
+        response = api_client.post(url, {'document_id': document.pk})
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert cabinet.documents.filter(pk=document.pk).exists()
+    
+    def test_remove_document_from_cabinet(self, api_client, user, cabinet, document):
+        """Тест удаления документа из кабинета."""
+        cabinet.documents.add(document)
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:cabinets-remove-document', args=[cabinet.pk])
+        response = api_client.post(url, {'document_id': document.pk})
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert not cabinet.documents.filter(pk=document.pk).exists()
+
+
+# =============================================================================
+# DOCUMENTCOMMENT VIEWSET TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestDocumentCommentViewSet:
+    """Тесты для DocumentCommentViewSet."""
+    
+    def test_create_comment(self, api_client, user, document):
+        """Тест создания комментария."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:document-comments-list')
+        
+        data = {
+            'document_id': document.pk,
+            'text': 'Test comment'
+        }
+        response = api_client.post(url, data)
+        
+        assert response.status_code == status.HTTP_201_CREATED
+        comment = DocumentComment.objects.get(document=document)
+        assert comment.text == 'Test comment'
+        assert comment.author == user
+    
+    def test_create_reply(self, api_client, user, document):
+        """Тест создания ответа на комментарий."""
+        parent = DocumentComment.objects.create(
+            document=document,
+            author=user,
+            text='Parent comment'
+        )
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:document-comments-list')
+        data = {
+            'document_id': document.pk,
+            'parent_id': parent.pk,
+            'text': 'Reply comment'
+        }
+        response = api_client.post(url, data)
+        
+        assert response.status_code == status.HTTP_201_CREATED
+        reply = DocumentComment.objects.get(parent=parent)
+        assert reply.text == 'Reply comment'
+        assert reply.depth == 1
+    
+    def test_update_comment(self, api_client, user, document):
+        """Тест обновления комментария."""
+        comment = DocumentComment.objects.create(
+            document=document,
+            author=user,
+            text='Original text'
+        )
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:document-comments-detail', args=[comment.pk])
+        response = api_client.patch(url, {'text': 'Updated text'})
+        
+        assert response.status_code == status.HTTP_200_OK
+        comment.refresh_from_db()
+        assert comment.text == 'Updated text'
+        assert comment.is_edited is True
+    
+    def test_delete_own_comment(self, api_client, user, document):
+        """Тест удаления своего комментария."""
+        comment = DocumentComment.objects.create(
+            document=document,
+            author=user,
+            text='Test'
+        )
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:document-comments-detail', args=[comment.pk])
+        response = api_client.delete(url)
+        
+        assert response.status_code == status.HTTP_204_NO_CONTENT
+        assert not DocumentComment.objects.filter(pk=comment.pk).exists()
+    
+    def test_cannot_delete_others_comment(self, api_client, user, staff_user, document):
+        """Тест запрета удаления чужого комментария."""
+        comment = DocumentComment.objects.create(
+            document=document,
+            author=staff_user,
+            text='Test'
+        )
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:document-comments-detail', args=[comment.pk])
+        response = api_client.delete(url)
+        
+        assert response.status_code == status.HTTP_403_FORBIDDEN
+
+
+# =============================================================================
+# RELATED DOCUMENTS TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestRelatedDocuments:
+    """Тесты для связанных документов."""
+    
+    def test_add_related_document(self, api_client, user, document):
+        """Тест добавления связанного документа."""
+        related_doc = Document.objects.create(
+            title='Related Doc',
+            uploaded_by=user
+        )
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:documents-add-related', args=[document.pk])
+        response = api_client.post(url, {'document_id': related_doc.pk})
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert document.related_documents.filter(pk=related_doc.pk).exists()
+    
+    def test_list_related_documents(self, api_client, user, document):
+        """Тест получения списка связанных документов."""
+        related_doc = Document.objects.create(
+            title='Related Doc',
+            uploaded_by=user
+        )
+        document.related_documents.add(related_doc)
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:documents-related', args=[document.pk])
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert len(response.data) == 1
+    
+    def test_remove_related_document(self, api_client, user, document):
+        """Тест удаления связанного документа."""
+        related_doc = Document.objects.create(
+            title='Related Doc',
+            uploaded_by=user
+        )
+        document.related_documents.add(related_doc)
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:documents-remove-related', args=[document.pk])
+        response = api_client.post(url, {'document_id': related_doc.pk})
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert not document.related_documents.filter(pk=related_doc.pk).exists()
+    
+    def test_cannot_link_to_self(self, api_client, user, document):
+        """Тест запрета связывания документа с самим собой."""
+        api_client.force_authenticate(user=user)
+        
+        url = reverse('v1:documents-add-related', args=[document.pk])
+        response = api_client.post(url, {'document_id': document.pk})
+        
+        assert response.status_code == status.HTTP_400_BAD_REQUEST
+
+
+# =============================================================================
+# DJANGO-REVERSION TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestReversionEndpoints:
+    """Тесты для endpoints django-reversion."""
+    
+    def test_get_versions(self, api_client, user, document):
+        """Тест получения истории версий."""
+        # Создаем версию через изменение
+        document.title = 'Updated Title'
+        document.save()
+        
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:documents-versions', args=[document.pk])
+        
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        # Должна быть хотя бы одна версия
+        assert len(response.data) >= 1
+    
+    def test_get_activity(self, api_client, user, document):
+        """Тест получения activity timeline."""
+        api_client.force_authenticate(user=user)
+        url = reverse('v1:documents-activity', args=[document.pk])
+        
+        response = api_client.get(url)
+        
+        assert response.status_code == status.HTTP_200_OK
+        assert isinstance(response.data, list)
+
+
+# =============================================================================
+# INTEGRATION TESTS
+# =============================================================================
+
+@pytest.mark.django_db
+class TestIntegration:
+    """Интеграционные тесты."""
+    
+    def test_document_with_all_features(self, api_client, user, document_tag, document_type, cabinet):
+        """Тест документа со всеми фичами."""
+        api_client.force_authenticate(user=user)
+        
+        # Создаем документ
+        document = Document.objects.create(
+            title='Complex Document',
+            uploaded_by=user,
+            document_type=document_type
+        )
+        
+        # Добавляем тег
+        document_tag.documents.add(document)
+        
+        # Добавляем в кабинет
+        cabinet.documents.add(document)
+        
+        # Создаем комментарий
+        DocumentComment.objects.create(
+            document=document,
+            author=user,
+            text='Test comment'
+        )
+        
+        # Проверяем, что все связано
+        assert document.document_type == document_type
+        assert document_tag in document.tags.all()
+        assert document in cabinet.documents.all()
+        assert document.comments.count() == 1