test(analyzer,serp): add tests for caching, single query, and parallel processing

- Add TestSingleQueryBugFix: verify SERP.query called once per analysis
- Add TestPatentCaching: DB cache hit/miss, SERP query cache hit/miss
- Add TestDynamicDateRange: rolling window, days_back param
- Add TestFilesystemPDFCaching: skip download, redownload empty files
- Add autouse mock_db fixture to prevent real DB connections in all tests

tests/test_serp_api.py

@@ -1,7 +1,11 @@
 """Tests for SERP API patent retrieval and parsing functionality."""
 
+import os
 import pytest
+from unittest.mock import patch, Mock
+from datetime import datetime, timedelta
 from SPARC.serp_api import SERP
+from SPARC.types import Patent
 
 
 class TestTextCleaning:
@@ -176,3 +180,89 @@ class TestPatentMinimization:
 
         # Sections should be separated by double newlines
         assert "\n\n" in result
+
+
+class TestDynamicDateRange:
+    """Test dynamic date range computation in SERP.query."""
+
+    def test_query_uses_rolling_date_window(self, mocker):
+        """Verify the date filter uses a rolling window, not hardcoded dates."""
+        mock_search = mocker.patch("SPARC.serp_api.serpapi.search")
+        mock_search.return_value = {"organic_results": []}
+        mocker.patch("SPARC.serp_api.config.api_key", "fake-key")
+        mocker.patch("SPARC.serp_api.config.patent_search_days", 90)
+
+        SERP.query("TestCorp")
+
+        call_params = mock_search.call_args[0][0]
+        tbs = call_params["tbs"]
+        # Should contain "cdr:1,cd_min:" with a date, not the old hardcoded one
+        assert "cdr:1,cd_min:" in tbs
+        assert "10/28/2025" not in tbs  # old hardcoded date gone
+
+    def test_query_respects_days_back_param(self, mocker):
+        """Verify days_back parameter controls the date window."""
+        mock_search = mocker.patch("SPARC.serp_api.serpapi.search")
+        mock_search.return_value = {"organic_results": []}
+        mocker.patch("SPARC.serp_api.config.api_key", "fake-key")
+        mocker.patch("SPARC.serp_api.config.patent_search_days", 90)
+
+        now = datetime.now()
+        SERP.query("TestCorp", days_back=30)
+
+        call_params = mock_search.call_args[0][0]
+        tbs = call_params["tbs"]
+        expected_start = (now - timedelta(days=30)).strftime("%-m/%-d/%Y")
+        assert expected_start in tbs
+
+
+class TestFilesystemPDFCaching:
+    """Test that save_patents skips download for existing files."""
+
+    def test_save_patents_skips_download_when_cached(self, mocker, tmp_path):
+        """Already-downloaded PDFs should not be re-downloaded."""
+        mock_get = mocker.patch("SPARC.serp_api.requests.get")
+        mocker.patch("SPARC.serp_api.os.makedirs")
+
+        pdf_path = tmp_path / "US123.pdf"
+        pdf_path.write_bytes(b"%PDF-1.4 fake content")
+
+        mocker.patch("SPARC.serp_api.os.path.exists", return_value=True)
+        mocker.patch("SPARC.serp_api.os.path.getsize", return_value=100)
+
+        patent = Patent(patent_id="US123", pdf_link="http://example.com/test.pdf")
+        result = SERP.save_patents(patent)
+
+        mock_get.assert_not_called()
+        assert result.pdf_path == "patents/US123.pdf"
+
+    def test_save_patents_downloads_when_not_cached(self, mocker):
+        """Missing PDFs should be downloaded."""
+        mock_response = Mock()
+        mock_response.content = b"%PDF-1.4 content"
+        mock_get = mocker.patch("SPARC.serp_api.requests.get", return_value=mock_response)
+        mocker.patch("SPARC.serp_api.os.makedirs")
+        mocker.patch("SPARC.serp_api.os.path.exists", return_value=False)
+        mock_open = mocker.patch("builtins.open", mocker.mock_open())
+
+        patent = Patent(patent_id="US456", pdf_link="http://example.com/test.pdf")
+        result = SERP.save_patents(patent)
+
+        mock_get.assert_called_once_with("http://example.com/test.pdf")
+        assert result.pdf_path == "patents/US456.pdf"
+
+    def test_save_patents_redownloads_empty_files(self, mocker):
+        """Empty/corrupt PDFs (0 bytes) should be re-downloaded."""
+        mock_response = Mock()
+        mock_response.content = b"%PDF-1.4 content"
+        mock_get = mocker.patch("SPARC.serp_api.requests.get", return_value=mock_response)
+        mocker.patch("SPARC.serp_api.os.makedirs")
+        mocker.patch("SPARC.serp_api.os.path.exists", return_value=True)
+        mocker.patch("SPARC.serp_api.os.path.getsize", return_value=0)
+        mock_open = mocker.patch("builtins.open", mocker.mock_open())
+
+        patent = Patent(patent_id="US789", pdf_link="http://example.com/test.pdf")
+        result = SERP.save_patents(patent)
+
+        mock_get.assert_called_once()
+        assert result.pdf_path == "patents/US789.pdf"