diff --git a/tests/test_processors/test_download.py b/tests/test_processors/test_download.py
new file mode 100644
index 0000000..63860db
--- /dev/null
+++ b/tests/test_processors/test_download.py
@@ -0,0 +1,127 @@
+"""Tests for DownloadProcessor and DownloadInput/DownloadOutput schemas.
+
+Test coverage:
+- DownloadInput schema validation
+- DownloadOutput schema validation
+- DownloadProcessor metadata fetching
+- DownloadProcessor content downloading
+- DownloadProcessor state recording
+"""
+
+import pytest
+from datetime import datetime
+from unittest.mock import AsyncMock, MagicMock, patch
+from pathlib import Path
+
+from kb_pipeline.schemas import DownloadInput, DownloadOutput
+
+
+class TestDownloadInputSchema:
+    """Tests for DownloadInput schema validation."""
+
+    def test_schema_download_input_validates_required_fields(self):
+        """Test 1: DownloadInput validates required fields"""
+        # Test with all required fields
+        input_data = DownloadInput(
+            content_id="BV1xx",
+            platform="bilibili",
+            content_dir="/tmp/content",
+            content_type="video"
+        )
+        assert input_data.content_id == "BV1xx"
+        assert input_data.platform == "bilibili"
+        assert input_data.content_dir == "/tmp/content"
+        assert input_data.content_type == "video"
+
+    def test_schema_download_input_requires_content_dir(self):
+        """DownloadInput should require content_dir"""
+        with pytest.raises(Exception):  # ValidationError from pydantic
+            DownloadInput(
+                content_id="BV1xx",
+                platform="bilibili",
+                content_type="video"
+                # Missing content_dir
+            )
+
+    def test_schema_download_input_requires_content_type(self):
+        """DownloadInput should require content_type"""
+        with pytest.raises(Exception):  # ValidationError from pydantic
+            DownloadInput(
+                content_id="BV1xx",
+                platform="bilibili",
+                content_dir="/tmp/content"
+                # Missing content_type
+            )
+
+
+class TestDownloadOutputSchema:
+    """Tests for DownloadOutput schema validation."""
+
+    def test_schema_download_output_validates_required_fields(self):
+        """Test 2: DownloadOutput validates required fields"""
+        output = DownloadOutput(
+            success=True,
+            metadata_file="/tmp/content/bilibili_BV1xx_metadata.json",
+            content_file="/tmp/content/bilibili_BV1xx_content.md",
+            title="Test Video",
+            author="Test Author"
+        )
+        assert output.success is True
+        assert output.metadata_file == "/tmp/content/bilibili_BV1xx_metadata.json"
+        assert output.content_file == "/tmp/content/bilibili_BV1xx_content.md"
+        assert output.title == "Test Video"
+        assert output.author == "Test Author"
+        assert output.duration is None  # Optional field
+
+    def test_schema_download_output_handles_video_content_type(self):
+        """Test 3: DownloadOutput handles video content type with duration"""
+        output = DownloadOutput(
+            success=True,
+            metadata_file="/tmp/content/bilibili_BV1xx_metadata.json",
+            content_file="",  # Video content handled by ASR
+            title="Test Video",
+            author="Test Author",
+            duration=300  # 5 minutes
+        )
+        assert output.success is True
+        assert output.duration == 300
+        assert output.content_file == ""
+
+    def test_schema_download_output_handles_article_content_type(self):
+        """Test 3: DownloadOutput handles article content type without duration"""
+        output = DownloadOutput(
+            success=True,
+            metadata_file="/tmp/content/bilibili_CV123_metadata.json",
+            content_file="/tmp/content/bilibili_CV123_content.md",
+            title="Test Article",
+            author="Test Author",
+            duration=None  # Articles don't have duration
+        )
+        assert output.success is True
+        assert output.duration is None
+        assert output.content_file == "/tmp/content/bilibili_CV123_content.md"
+
+    def test_schema_download_output_handles_zhihu_answer(self):
+        """Test 3: DownloadOutput handles Zhihu answer content type"""
+        output = DownloadOutput(
+            success=True,
+            metadata_file="/tmp/content/zhihu_123456_metadata.json",
+            content_file="/tmp/content/zhihu_123456_content.md",
+            title="Test Answer",
+            author="Test Author"
+        )
+        assert output.success is True
+        assert "zhihu" in output.metadata_file
+
+    def test_schema_download_output_handles_failure(self):
+        """DownloadOutput should handle failure case"""
+        output = DownloadOutput(
+            success=False,
+            error_message="Network error",
+            metadata_file="",
+            content_file="",
+            title="",
+            author=""
+        )
+        assert output.success is False
+        assert output.error_message == "Network error"