diff --git a/backend/tests/services/test_direct_extraction_engine.py b/backend/tests/services/test_direct_extraction_engine.py
new file mode 100644
index 0000000..f0b4256
--- /dev/null
+++ b/backend/tests/services/test_direct_extraction_engine.py
@@ -0,0 +1,604 @@
+"""
+Unit tests for DirectExtractionEngine service.
+
+Tests cover:
+- Text extraction accuracy
+- Structure preservation (headers, lists, sections)
+- Coordinate extraction
+- Table detection
+- Image extraction
+"""
+
+import pytest
+from pathlib import Path
+import fitz
+from PIL import Image
+import io
+
+from app.services.direct_extraction_engine import DirectExtractionEngine
+from app.models.unified_document import (
+    ElementType, ProcessingTrack, UnifiedDocument
+)
+
+
+class TestDirectExtractionEngine:
+    """Test suite for DirectExtractionEngine."""
+
+    @pytest.fixture
+    def engine(self):
+        """Create engine with default settings."""
+        return DirectExtractionEngine()
+
+    @pytest.fixture
+    def engine_no_tables(self):
+        """Create engine with table detection disabled."""
+        return DirectExtractionEngine(enable_table_detection=False)
+
+    @pytest.fixture
+    def engine_no_images(self):
+        """Create engine with image extraction disabled."""
+        return DirectExtractionEngine(enable_image_extraction=False)
+
+    # ===== Text Extraction Tests =====
+
+    def test_extract_simple_text(self, engine, temp_dir):
+        """Test basic text extraction from PDF."""
+        pdf_path = temp_dir / "simple.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        test_text = "Hello World! This is a test document."
+        page.insert_text((50, 50), test_text, fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        assert isinstance(result, UnifiedDocument)
+        assert len(result.pages) == 1
+        assert result.metadata.processing_track == ProcessingTrack.DIRECT
+
+        # Check text was extracted
+        text_elements = [e for e in result.pages[0].elements if e.is_text]
+        assert len(text_elements) > 0
+
+        # Verify text content
+        all_text = " ".join(e.content for e in text_elements if isinstance(e.content, str))
+        assert "Hello World" in all_text
+
+    def test_extract_multiline_text(self, engine, temp_dir):
+        """Test extraction of multiple lines of text."""
+        pdf_path = temp_dir / "multiline.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        lines = [
+            "First line of text",
+            "Second line of text",
+            "Third line of text"
+        ]
+
+        y = 50
+        for line in lines:
+            page.insert_text((50, y), line, fontsize=12)
+            y += 20
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        text_elements = [e for e in result.pages[0].elements if e.is_text]
+        all_text = " ".join(e.content for e in text_elements if isinstance(e.content, str))
+
+        for line in lines:
+            assert line in all_text
+
+    def test_extract_chinese_text(self, engine, temp_dir):
+        """Test extraction of Chinese text."""
+        pdf_path = temp_dir / "chinese.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Use a font that supports Chinese if available
+        chinese_text = "這是中文測試文字"
+        try:
+            page.insert_text((50, 50), chinese_text, fontsize=12)
+            doc.save(str(pdf_path))
+            doc.close()
+
+            result = engine.extract(pdf_path)
+            assert len(result.pages) == 1
+        except Exception:
+            # Skip if font not available
+            doc.close()
+            pytest.skip("Chinese font not available for test")
+
+    def test_extract_multiple_pages(self, engine, temp_dir):
+        """Test extraction from multi-page PDF."""
+        pdf_path = temp_dir / "multipage.pdf"
+        doc = fitz.open()
+
+        for i in range(5):
+            page = doc.new_page()
+            page.insert_text((50, 50), f"This is page {i + 1}", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        assert len(result.pages) == 5
+
+        for i, page in enumerate(result.pages):
+            assert page.page_number == i + 1
+
+    # ===== Coordinate Extraction Tests =====
+
+    def test_bounding_box_accuracy(self, engine, temp_dir):
+        """Test that bounding boxes are extracted correctly."""
+        pdf_path = temp_dir / "bbox.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Insert text at known position
+        x, y = 100, 200
+        page.insert_text((x, y), "Positioned Text", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        text_elements = [e for e in result.pages[0].elements if e.is_text]
+        assert len(text_elements) > 0
+
+        # Check that bbox is near the insertion point
+        element = text_elements[0]
+        assert element.bbox is not None
+        assert element.bbox.x0 >= 0
+        assert element.bbox.y0 >= 0
+        assert element.bbox.x1 > element.bbox.x0
+        assert element.bbox.y1 > element.bbox.y0
+
+    def test_page_dimensions(self, engine, temp_dir):
+        """Test that page dimensions are extracted correctly."""
+        pdf_path = temp_dir / "dimensions.pdf"
+        doc = fitz.open()
+
+        # Create A4 page (595.28 x 841.89 points)
+        page = doc.new_page(width=595.28, height=841.89)
+        page.insert_text((50, 50), "Test", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        dimensions = result.pages[0].dimensions
+        assert abs(dimensions.width - 595.28) < 1
+        assert abs(dimensions.height - 841.89) < 1
+
+    # ===== Structure Preservation Tests =====
+
+    def test_detect_title_by_font_size(self, engine, temp_dir):
+        """Test title detection based on font size."""
+        pdf_path = temp_dir / "title.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Large text for title
+        page.insert_text((50, 50), "Document Title", fontsize=24)
+        # Normal text for content
+        page.insert_text((50, 100), "This is regular content.", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        elements = result.pages[0].elements
+
+        # Should have extracted text elements
+        text_elements = [e for e in elements if e.is_text]
+        assert len(text_elements) >= 1
+
+        # Check that elements with larger fonts have different types or metadata
+        # Note: Title detection depends on font size thresholds and may vary
+        font_sizes = []
+        for e in text_elements:
+            if e.style and e.style.font_size:
+                font_sizes.append(e.style.font_size)
+
+        # Should have captured different font sizes
+        if len(font_sizes) >= 2:
+            assert max(font_sizes) > min(font_sizes)
+
+    def test_detect_list_items(self, engine, temp_dir):
+        """Test detection of list items."""
+        pdf_path = temp_dir / "list.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        y = 50
+        list_items = [
+            "• First item",
+            "• Second item",
+            "• Third item"
+        ]
+
+        for item in list_items:
+            page.insert_text((50, y), item, fontsize=12)
+            y += 20
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        list_elements = [e for e in result.pages[0].elements
+                        if e.type == ElementType.LIST_ITEM]
+
+        # Should detect list items
+        assert len(list_elements) >= 1
+
+    def test_detect_headers_footers(self, engine, temp_dir):
+        """Test header/footer detection by position."""
+        pdf_path = temp_dir / "header_footer.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Header at top
+        page.insert_text((50, 30), "Document Header", fontsize=10)
+
+        # Content in middle
+        page.insert_text((50, 400), "Main content of the document.", fontsize=12)
+
+        # Footer at bottom
+        page.insert_text((50, 800), "Page 1", fontsize=10)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        elements = result.pages[0].elements
+
+        # Check for header/footer metadata
+        headers = [e for e in elements if e.metadata.get('is_page_header')]
+        footers = [e for e in elements if e.metadata.get('is_page_footer')]
+
+        # At least one should be detected
+        assert len(headers) + len(footers) >= 1
+
+    def test_section_hierarchy(self, engine, temp_dir):
+        """Test section hierarchy building."""
+        pdf_path = temp_dir / "sections.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Create hierarchical headers
+        page.insert_text((50, 50), "Main Title", fontsize=20)
+        page.insert_text((50, 100), "Section 1", fontsize=16)
+        page.insert_text((50, 150), "Subsection 1.1", fontsize=14)
+        page.insert_text((50, 200), "Content text", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        elements = result.pages[0].elements
+
+        # Check for section levels
+        headers = [e for e in elements
+                  if e.type in [ElementType.TITLE, ElementType.HEADER]]
+
+        levels = [e.metadata.get('section_level') for e in headers
+                 if e.metadata.get('section_level')]
+
+        if levels:
+            # Should have multiple levels
+            assert len(set(levels)) >= 1
+
+    # ===== Table Detection Tests =====
+
+    def test_detect_simple_table(self, engine, temp_dir):
+        """Test detection of a simple table."""
+        pdf_path = temp_dir / "table.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Create a simple table layout
+        table_data = [
+            ["Name", "Age", "City"],
+            ["Alice", "30", "Tokyo"],
+            ["Bob", "25", "Paris"]
+        ]
+
+        y = 100
+        for row in table_data:
+            x = 50
+            for cell in row:
+                page.insert_text((x, y), cell, fontsize=10)
+                x += 100
+            y += 20
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        table_elements = [e for e in result.pages[0].elements
+                        if e.type == ElementType.TABLE]
+
+        # Table detection may or may not succeed depending on layout
+        # Just verify the extraction completed without error
+        assert result.pages[0].elements is not None
+
+    def test_table_detection_disabled(self, engine_no_tables, temp_dir):
+        """Test that table detection can be disabled."""
+        pdf_path = temp_dir / "no_table.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Create table-like layout
+        for i in range(3):
+            page.insert_text((50 + i*100, 100), f"Col{i}", fontsize=10)
+            page.insert_text((50 + i*100, 120), f"Val{i}", fontsize=10)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine_no_tables.extract(pdf_path)
+
+        # With table detection disabled, should not find tables
+        table_elements = [e for e in result.pages[0].elements
+                        if e.type == ElementType.TABLE]
+
+        assert len(table_elements) == 0
+
+    # ===== Image Extraction Tests =====
+
+    def test_extract_embedded_image(self, engine, temp_dir):
+        """Test extraction of embedded images."""
+        pdf_path = temp_dir / "with_image.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Create and embed an image
+        img = Image.new('RGB', (100, 100), color='red')
+        img_bytes = io.BytesIO()
+        img.save(img_bytes, format='PNG')
+        img_bytes.seek(0)
+
+        # Insert image into PDF
+        rect = fitz.Rect(100, 100, 300, 300)
+        page.insert_image(rect, stream=img_bytes.read())
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        # Create output directory for images
+        output_dir = temp_dir / "images"
+
+        result = engine.extract(pdf_path, output_dir)
+
+        image_elements = [e for e in result.pages[0].elements
+                        if e.type == ElementType.IMAGE]
+
+        assert len(image_elements) >= 1
+
+        # Check image has bbox
+        if image_elements:
+            img_elem = image_elements[0]
+            assert img_elem.bbox is not None
+
+    def test_image_extraction_disabled(self, engine_no_images, temp_dir):
+        """Test that image extraction can be disabled."""
+        pdf_path = temp_dir / "no_image.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Add image
+        img = Image.new('RGB', (50, 50), color='blue')
+        img_bytes = io.BytesIO()
+        img.save(img_bytes, format='PNG')
+        img_bytes.seek(0)
+
+        rect = fitz.Rect(100, 100, 200, 200)
+        page.insert_image(rect, stream=img_bytes.read())
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine_no_images.extract(pdf_path)
+
+        image_elements = [e for e in result.pages[0].elements
+                        if e.type == ElementType.IMAGE]
+
+        assert len(image_elements) == 0
+
+    # ===== Metadata Tests =====
+
+    def test_extract_pdf_metadata(self, engine, temp_dir):
+        """Test extraction of PDF metadata."""
+        pdf_path = temp_dir / "metadata.pdf"
+        doc = fitz.open()
+
+        # Set metadata
+        doc.set_metadata({
+            "title": "Test Document",
+            "author": "Test Author",
+            "subject": "Testing"
+        })
+
+        page = doc.new_page()
+        page.insert_text((50, 50), "Content", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        assert result.metadata.title == "Test Document"
+        assert result.metadata.author == "Test Author"
+        assert result.metadata.subject == "Testing"
+
+    def test_processing_track_is_direct(self, engine, temp_dir):
+        """Test that processing track is set to DIRECT."""
+        pdf_path = temp_dir / "track.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        assert result.metadata.processing_track == ProcessingTrack.DIRECT
+
+    def test_confidence_is_perfect(self, engine, temp_dir):
+        """Test that direct extraction has confidence 1.0."""
+        pdf_path = temp_dir / "confidence.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "High confidence text", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        text_elements = [e for e in result.pages[0].elements if e.is_text]
+
+        for element in text_elements:
+            assert element.confidence == 1.0
+
+    # ===== Style Extraction Tests =====
+
+    def test_extract_font_info(self, engine, temp_dir):
+        """Test extraction of font information."""
+        pdf_path = temp_dir / "fonts.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        page.insert_text((50, 50), "Normal text", fontsize=12)
+        page.insert_text((50, 80), "Large text", fontsize=20)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        text_elements = [e for e in result.pages[0].elements
+                        if e.is_text and e.style]
+
+        # Should have style information
+        assert len(text_elements) > 0
+
+        # Check font sizes are different
+        font_sizes = [e.style.font_size for e in text_elements if e.style.font_size]
+        if len(font_sizes) >= 2:
+            assert max(font_sizes) > min(font_sizes)
+
+    # ===== Error Handling Tests =====
+
+    def test_nonexistent_file(self, engine, temp_dir):
+        """Test handling of non-existent file."""
+        pdf_path = temp_dir / "nonexistent.pdf"
+
+        result = engine.extract(pdf_path)
+
+        # Should return document with errors
+        assert result.processing_errors is not None
+        assert len(result.processing_errors) > 0
+
+    def test_corrupted_pdf(self, engine, temp_dir):
+        """Test handling of corrupted PDF."""
+        pdf_path = temp_dir / "corrupted.pdf"
+
+        # Create invalid PDF file
+        pdf_path.write_bytes(b"This is not a valid PDF file")
+
+        result = engine.extract(pdf_path)
+
+        # Should return document with errors
+        assert result.processing_errors is not None
+
+    def test_empty_pdf_page(self, engine, temp_dir):
+        """Test handling of PDF with empty pages."""
+        pdf_path = temp_dir / "empty_page.pdf"
+        doc = fitz.open()
+        doc.new_page()  # Empty page
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        assert len(result.pages) == 1
+        # May or may not have elements
+
+    # ===== Link Extraction Tests =====
+
+    def test_extract_hyperlinks(self, engine, temp_dir):
+        """Test extraction of hyperlinks."""
+        pdf_path = temp_dir / "links.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        # Add text and link
+        page.insert_text((50, 50), "Click here", fontsize=12)
+
+        # Add hyperlink
+        link_rect = fitz.Rect(50, 40, 120, 60)
+        page.insert_link({
+            'kind': fitz.LINK_URI,
+            'from': link_rect,
+            'uri': 'https://example.com'
+        })
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = engine.extract(pdf_path)
+
+        reference_elements = [e for e in result.pages[0].elements
+                            if e.type == ElementType.REFERENCE]
+
+        assert len(reference_elements) >= 1
+
+        # Check URI is extracted
+        if reference_elements:
+            link = reference_elements[0]
+            assert link.content.get('uri') == 'https://example.com'
+
+    # ===== Performance Tests =====
+
+    def test_large_document_performance(self, engine, temp_dir):
+        """Test extraction performance on larger document."""
+        import time
+
+        pdf_path = temp_dir / "large.pdf"
+        doc = fitz.open()
+
+        # Create 20 pages with content
+        for i in range(20):
+            page = doc.new_page()
+            for j in range(10):
+                page.insert_text((50, 50 + j*20),
+                               f"Page {i+1} Line {j+1}: Lorem ipsum dolor sit amet",
+                               fontsize=10)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        start_time = time.time()
+        result = engine.extract(pdf_path)
+        elapsed = time.time() - start_time
+
+        assert len(result.pages) == 20
+        assert elapsed < 30  # Should complete within 30 seconds
+
+        # Check processing time is recorded
+        assert result.metadata.processing_time > 0
diff --git a/backend/tests/services/test_dual_track_integration.py b/backend/tests/services/test_dual_track_integration.py
new file mode 100644
index 0000000..e583477
--- /dev/null
+++ b/backend/tests/services/test_dual_track_integration.py
@@ -0,0 +1,471 @@
+"""
+Integration tests for dual-track document processing.
+
+Tests cover:
+- Routing logic between OCR and Direct tracks
+- UnifiedDocument generation from both tracks
+- Backward compatibility with legacy formats
+"""
+
+import pytest
+from pathlib import Path
+import fitz
+from PIL import Image
+import io
+import json
+
+from app.services.document_type_detector import DocumentTypeDetector, DocumentType
+from app.services.direct_extraction_engine import DirectExtractionEngine
+from app.models.unified_document import (
+    UnifiedDocument, ProcessingTrack, ElementType
+)
+from app.services.unified_document_exporter import UnifiedDocumentExporter, ExportFormat
+
+
+class TestDualTrackRouting:
+    """Test routing logic between OCR and Direct tracks."""
+
+    @pytest.fixture
+    def detector(self):
+        """Create document type detector."""
+        return DocumentTypeDetector()
+
+    # ===== Routing Tests =====
+
+    def test_route_editable_pdf_to_direct(self, detector, temp_dir):
+        """Test that editable PDFs are routed to direct track."""
+        pdf_path = temp_dir / "editable.pdf"
+        doc = fitz.open()
+
+        for i in range(3):
+            page = doc.new_page()
+            page.insert_text((50, 50), f"Page {i+1}: " + "Text content " * 20, fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = detector.detect(pdf_path)
+
+        assert result.track == "direct"
+        assert result.document_type == DocumentType.PDF_EDITABLE
+        assert result.confidence >= 0.9
+
+    def test_route_scanned_pdf_to_ocr(self, detector, temp_dir):
+        """Test that scanned PDFs are routed to OCR track."""
+        pdf_path = temp_dir / "scanned.pdf"
+        doc = fitz.open()
+
+        for i in range(3):
+            page = doc.new_page()
+            # Only images, no text
+            img = Image.new('RGB', (400, 300), color=(200, 200, 200))
+            img_bytes = io.BytesIO()
+            img.save(img_bytes, format='PNG')
+            img_bytes.seek(0)
+
+            rect = fitz.Rect(50, 50, 550, 750)
+            page.insert_image(rect, stream=img_bytes.read())
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = detector.detect(pdf_path)
+
+        assert result.track == "ocr"
+        assert result.document_type == DocumentType.PDF_SCANNED
+
+    def test_route_image_to_ocr(self, detector, temp_dir):
+        """Test that images are routed to OCR track."""
+        img_path = temp_dir / "image.png"
+        img = Image.new('RGB', (100, 100), color='red')
+        img.save(str(img_path))
+
+        result = detector.detect(img_path)
+
+        assert result.track == "ocr"
+        assert result.document_type == DocumentType.IMAGE
+        assert result.confidence == 1.0
+
+    def test_route_text_file_to_direct(self, detector, temp_dir):
+        """Test that text files are routed to direct track."""
+        txt_path = temp_dir / "text.txt"
+        txt_path.write_text("This is a plain text file.\n" * 10)
+
+        result = detector.detect(txt_path)
+
+        assert result.track == "direct"
+        assert result.document_type == DocumentType.TEXT
+
+    def test_route_mixed_pdf_to_ocr(self, detector, temp_dir):
+        """Test that mixed PDFs are routed to OCR track."""
+        pdf_path = temp_dir / "mixed.pdf"
+        doc = fitz.open()
+
+        # Page 1: Text
+        page = doc.new_page()
+        page.insert_text((50, 50), "Text content " * 20, fontsize=12)
+
+        # Page 2: Image only
+        page = doc.new_page()
+        img = Image.new('RGB', (400, 300), color=(200, 200, 200))
+        img_bytes = io.BytesIO()
+        img.save(img_bytes, format='PNG')
+        img_bytes.seek(0)
+        rect = fitz.Rect(50, 50, 550, 750)
+        page.insert_image(rect, stream=img_bytes.read())
+
+        # Page 3: Image only
+        page = doc.new_page()
+        img = Image.new('RGB', (400, 300), color=(150, 150, 150))
+        img_bytes = io.BytesIO()
+        img.save(img_bytes, format='PNG')
+        img_bytes.seek(0)
+        page.insert_image(rect, stream=img_bytes.read())
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = detector.detect(pdf_path)
+
+        assert result.track == "ocr"
+        assert result.document_type == DocumentType.PDF_MIXED
+
+
+class TestUnifiedDocumentGeneration:
+    """Test UnifiedDocument generation from both tracks."""
+
+    @pytest.fixture
+    def direct_engine(self):
+        """Create direct extraction engine."""
+        return DirectExtractionEngine()
+
+    # ===== Direct Track Generation =====
+
+    def test_direct_track_generates_unified_document(self, direct_engine, temp_dir):
+        """Test that direct track generates valid UnifiedDocument."""
+        pdf_path = temp_dir / "test.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Test content", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        assert isinstance(result, UnifiedDocument)
+        assert result.document_id is not None
+        assert result.metadata is not None
+        assert len(result.pages) == 1
+
+    def test_unified_document_has_required_fields(self, direct_engine, temp_dir):
+        """Test that UnifiedDocument has all required fields."""
+        pdf_path = temp_dir / "complete.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Complete document", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        # Check metadata
+        assert result.metadata.filename == "complete.pdf"
+        assert result.metadata.file_type == "pdf"
+        assert result.metadata.processing_track == ProcessingTrack.DIRECT
+        assert result.metadata.processing_time >= 0
+
+        # Check page structure
+        page = result.pages[0]
+        assert page.page_number == 1
+        assert page.dimensions is not None
+        assert page.elements is not None
+
+    def test_elements_have_required_fields(self, direct_engine, temp_dir):
+        """Test that elements have all required fields."""
+        pdf_path = temp_dir / "elements.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Element test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        for element in result.pages[0].elements:
+            assert element.element_id is not None
+            assert element.type is not None
+            assert element.bbox is not None
+
+
+class TestUnifiedDocumentExport:
+    """Test UnifiedDocument export functionality."""
+
+    @pytest.fixture
+    def exporter(self):
+        """Create exporter."""
+        return UnifiedDocumentExporter()
+
+    @pytest.fixture
+    def sample_document(self, temp_dir):
+        """Create a sample UnifiedDocument."""
+        engine = DirectExtractionEngine()
+
+        pdf_path = temp_dir / "sample.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Sample document for export", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        return engine.extract(pdf_path)
+
+    def test_export_to_json(self, exporter, sample_document, temp_dir):
+        """Test export to JSON format."""
+        output_path = temp_dir / "output.json"
+
+        exporter.export_to_json(sample_document, output_path)
+
+        assert output_path.exists()
+
+        # Verify JSON is valid
+        with open(output_path) as f:
+            data = json.load(f)
+
+        assert "document_id" in data
+        assert "metadata" in data
+        assert "pages" in data
+
+    def test_export_to_markdown(self, exporter, sample_document, temp_dir):
+        """Test export to Markdown format."""
+        output_path = temp_dir / "output.md"
+
+        exporter.export_to_markdown(sample_document, output_path)
+
+        assert output_path.exists()
+
+        content = output_path.read_text()
+        assert len(content) > 0
+
+    def test_export_to_text(self, exporter, sample_document):
+        """Test export to plain text."""
+        text = exporter.export_to_text(sample_document)
+
+        assert isinstance(text, str)
+        assert len(text) > 0
+
+    def test_export_legacy_format(self, exporter, sample_document, temp_dir):
+        """Test export to legacy JSON format for backward compatibility."""
+        output_path = temp_dir / "legacy.json"
+
+        exporter.export_to_legacy_json(sample_document, output_path)
+
+        assert output_path.exists()
+
+        with open(output_path) as f:
+            data = json.load(f)
+
+        # Legacy format should have different structure
+        assert isinstance(data, (dict, list))
+
+
+class TestBackwardCompatibility:
+    """Test backward compatibility with existing system."""
+
+    @pytest.fixture
+    def direct_engine(self):
+        """Create direct extraction engine."""
+        return DirectExtractionEngine()
+
+    def test_document_can_be_serialized(self, direct_engine, temp_dir):
+        """Test that UnifiedDocument can be serialized to dict."""
+        pdf_path = temp_dir / "serialize.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Serializable", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        # Should be serializable
+        doc_dict = result.to_dict()
+
+        assert isinstance(doc_dict, dict)
+        assert "document_id" in doc_dict
+        assert "metadata" in doc_dict
+        assert "pages" in doc_dict
+
+    def test_element_types_are_strings(self, direct_engine, temp_dir):
+        """Test that element types serialize to strings."""
+        pdf_path = temp_dir / "types.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+        doc_dict = result.to_dict()
+
+        for page_data in doc_dict.get("pages", []):
+            for element in page_data.get("elements", []):
+                assert isinstance(element.get("type"), str)
+
+    def test_processing_track_is_string(self, direct_engine, temp_dir):
+        """Test that processing track serializes to string."""
+        pdf_path = temp_dir / "track.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Track test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+        doc_dict = result.to_dict()
+
+        track = doc_dict.get("metadata", {}).get("processing_track")
+        assert isinstance(track, str)
+        assert track in ["ocr", "direct", "hybrid", "auto"]
+
+
+class TestCrossTrackConsistency:
+    """Test consistency between OCR and Direct track outputs."""
+
+    @pytest.fixture
+    def detector(self):
+        """Create document type detector."""
+        return DocumentTypeDetector()
+
+    @pytest.fixture
+    def direct_engine(self):
+        """Create direct extraction engine."""
+        return DirectExtractionEngine()
+
+    def test_both_tracks_produce_unified_document(self, detector, direct_engine, temp_dir):
+        """Test that both tracks produce UnifiedDocument format."""
+        # Create editable PDF for direct track
+        pdf_path = temp_dir / "editable.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Editable content " * 20, fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        # Detect and route
+        detection = detector.detect(pdf_path)
+        assert detection.track == "direct"
+
+        # Extract
+        result = direct_engine.extract(pdf_path)
+
+        # Verify UnifiedDocument structure
+        assert isinstance(result, UnifiedDocument)
+        assert result.metadata.processing_track == ProcessingTrack.DIRECT
+
+    def test_metadata_structure_consistent(self, direct_engine, temp_dir):
+        """Test that metadata structure is consistent."""
+        pdf_path = temp_dir / "metadata.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Metadata test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+        metadata = result.metadata
+
+        # Required metadata fields
+        assert hasattr(metadata, 'filename')
+        assert hasattr(metadata, 'file_type')
+        assert hasattr(metadata, 'file_size')
+        assert hasattr(metadata, 'processing_track')
+        assert hasattr(metadata, 'processing_time')
+        assert hasattr(metadata, 'created_at')
+
+    def test_element_structure_consistent(self, direct_engine, temp_dir):
+        """Test that element structure is consistent."""
+        pdf_path = temp_dir / "elements.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+        page.insert_text((50, 50), "Element structure test", fontsize=12)
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        for element in result.pages[0].elements:
+            # Required element fields
+            assert hasattr(element, 'element_id')
+            assert hasattr(element, 'type')
+            assert hasattr(element, 'content')
+            assert hasattr(element, 'bbox')
+            assert hasattr(element, 'confidence')
+
+
+class TestEdgeCases:
+    """Test edge cases in dual-track processing."""
+
+    @pytest.fixture
+    def detector(self):
+        """Create document type detector."""
+        return DocumentTypeDetector()
+
+    @pytest.fixture
+    def direct_engine(self):
+        """Create direct extraction engine."""
+        return DirectExtractionEngine()
+
+    def test_empty_pdf(self, direct_engine, temp_dir):
+        """Test handling of empty PDF."""
+        pdf_path = temp_dir / "empty.pdf"
+        doc = fitz.open()
+        doc.new_page()
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        assert len(result.pages) == 1
+        # May or may not have elements
+
+    def test_very_small_file(self, detector, temp_dir):
+        """Test handling of very small files."""
+        small_file = temp_dir / "small.txt"
+        small_file.write_text("Hi")
+
+        result = detector.detect(small_file)
+
+        assert result.track in ["direct", "ocr"]
+
+    def test_special_characters_in_content(self, direct_engine, temp_dir):
+        """Test handling of special characters."""
+        pdf_path = temp_dir / "special.pdf"
+        doc = fitz.open()
+        page = doc.new_page()
+
+        special_text = "Special: © ® ™ € £ ¥ § ¶ • … — – '"
+        page.insert_text((50, 50), special_text, fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        # Should not crash
+        assert len(result.pages) == 1
+
+    def test_large_page_count(self, direct_engine, temp_dir):
+        """Test handling of document with many pages."""
+        pdf_path = temp_dir / "many_pages.pdf"
+        doc = fitz.open()
+
+        for i in range(50):
+            page = doc.new_page()
+            page.insert_text((50, 50), f"Page {i+1}", fontsize=12)
+
+        doc.save(str(pdf_path))
+        doc.close()
+
+        result = direct_engine.extract(pdf_path)
+
+        assert len(result.pages) == 50
diff --git a/openspec/changes/dual-track-document-processing/tasks.md b/openspec/changes/dual-track-document-processing/tasks.md
index eeb211a..3274890 100644
--- a/openspec/changes/dual-track-document-processing/tasks.md
+++ b/openspec/changes/dual-track-document-processing/tasks.md
@@ -115,18 +115,18 @@
     - Note: UI prepared with disabled state; awaiting Section 5 implementation
 
 ## 8. Testing
-- [ ] 8.1 Unit tests for DocumentTypeDetector
-  - [ ] 8.1.1 Test various file types
-  - [ ] 8.1.2 Test editability detection
-  - [ ] 8.1.3 Test edge cases
-- [ ] 8.2 Unit tests for DirectExtractionEngine
-  - [ ] 8.2.1 Test text extraction accuracy
-  - [ ] 8.2.2 Test structure preservation
-  - [ ] 8.2.3 Test coordinate extraction
-- [ ] 8.3 Integration tests for dual-track processing
-  - [ ] 8.3.1 Test routing logic
-  - [ ] 8.3.2 Test UnifiedDocument generation
-  - [ ] 8.3.3 Test backward compatibility
+- [x] 8.1 Unit tests for DocumentTypeDetector
+  - [x] 8.1.1 Test various file types
+  - [x] 8.1.2 Test editability detection
+  - [x] 8.1.3 Test edge cases
+- [x] 8.2 Unit tests for DirectExtractionEngine
+  - [x] 8.2.1 Test text extraction accuracy
+  - [x] 8.2.2 Test structure preservation
+  - [x] 8.2.3 Test coordinate extraction
+- [x] 8.3 Integration tests for dual-track processing
+  - [x] 8.3.1 Test routing logic
+  - [x] 8.3.2 Test UnifiedDocument generation
+  - [x] 8.3.3 Test backward compatibility
 - [ ] 8.4 End-to-end tests
   - [ ] 8.4.1 Test scanned PDF processing (OCR track)
   - [ ] 8.4.2 Test editable PDF processing (direct track)