Add comprehensive tests for Assets API (14 tests)

Tests include:
- Asset model validation (8 tests)
  - Asset, AssetRename, FolderCreate models
  - Field validation, filename validation
  - Size helper methods (size_mb, size_kb)
  - Slug normalization

- Sync AssetsEndpoint (6 tests)
  - List, get, rename, delete operations
  - Folder listing
  - Validation error handling

All 14 tests passing. Achieves comprehensive coverage for Assets API.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/models/test_asset.py

@@ -0,0 +1,96 @@
+"""Tests for Asset data models."""
+
+import pytest
+from pydantic import ValidationError
+
+from wikijs.models import Asset, AssetFolder, AssetRename, AssetMove, FolderCreate
+
+
+class TestAsset:
+    """Test Asset model."""
+
+    def test_asset_creation_minimal(self):
+        """Test creating an asset with minimal fields."""
+        asset = Asset(
+            id=1,
+            filename="test.png",
+            ext="png",
+            kind="image",
+            mime="image/png",
+            file_size=1024,
+            created_at="2024-01-01T00:00:00Z",
+            updated_at="2024-01-01T00:00:00Z",
+        )
+        assert asset.id == 1
+        assert asset.filename == "test.png"
+        assert asset.file_size == 1024
+
+    def test_asset_size_helpers(self):
+        """Test size helper methods."""
+        asset = Asset(
+            id=1,
+            filename="test.png",
+            ext="png",
+            kind="image",
+            mime="image/png",
+            file_size=1048576,  # 1 MB
+            created_at="2024-01-01T00:00:00Z",
+            updated_at="2024-01-01T00:00:00Z",
+        )
+        assert asset.size_mb == 1.0
+        assert asset.size_kb == 1024.0
+
+    def test_asset_filename_validation(self):
+        """Test filename validation."""
+        with pytest.raises(ValidationError):
+            Asset(
+                id=1,
+                filename="",
+                ext="png",
+                kind="image",
+                mime="image/png",
+                file_size=1024,
+                created_at="2024-01-01T00:00:00Z",
+                updated_at="2024-01-01T00:00:00Z",
+            )
+
+
+class TestAssetRename:
+    """Test AssetRename model."""
+
+    def test_asset_rename_valid(self):
+        """Test valid asset rename."""
+        rename = AssetRename(asset_id=1, new_filename="newname.png")
+        assert rename.asset_id == 1
+        assert rename.new_filename == "newname.png"
+
+    def test_asset_rename_validation(self):
+        """Test validation."""
+        with pytest.raises(ValidationError):
+            AssetRename(asset_id=0, new_filename="test.png")
+
+        with pytest.raises(ValidationError):
+            AssetRename(asset_id=1, new_filename="")
+
+
+class TestFolderCreate:
+    """Test FolderCreate model."""
+
+    def test_folder_create_valid(self):
+        """Test valid folder creation."""
+        folder = FolderCreate(slug="documents", name="Documents")
+        assert folder.slug == "documents"
+        assert folder.name == "Documents"
+
+    def test_folder_create_slug_validation(self):
+        """Test slug validation."""
+        with pytest.raises(ValidationError):
+            FolderCreate(slug="")
+
+        with pytest.raises(ValidationError):
+            FolderCreate(slug="///")
+
+    def test_folder_create_slug_normalization(self):
+        """Test slug normalization."""
+        folder = FolderCreate(slug="/documents/", name="Documents")
+        assert folder.slug == "documents"