test: add comprehensive tests across modules to increase coverage above 60%

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_extract_metadata.py

@@ -0,0 +1,40 @@
+"""Tests for app/tasks/extract_metadata_with_gpt.py module."""
+import pytest
+
+from app.tasks.extract_metadata_with_gpt import extract_json_from_text
+
+
+@pytest.mark.unit
+class TestExtractJsonFromText:
+    """Tests for extract_json_from_text function."""
+
+    def test_extracts_json_from_backticks(self):
+        """Test extraction of JSON from triple-backtick block."""
+        text = '```json\n{"key": "value"}\n```'
+        result = extract_json_from_text(text)
+        assert result == '{"key": "value"}'
+
+    def test_extracts_json_from_backticks_no_lang(self):
+        """Test extraction from backticks without language tag."""
+        text = '```\n{"key": "value"}\n```'
+        result = extract_json_from_text(text)
+        assert result == '{"key": "value"}'
+
+    def test_extracts_json_from_raw_text(self):
+        """Test extraction from raw text with JSON."""
+        text = 'Here is the result: {"key": "value"} end.'
+        result = extract_json_from_text(text)
+        assert result == '{"key": "value"}'
+
+    def test_returns_none_for_no_json(self):
+        """Test returns None when no JSON found."""
+        text = "No JSON here at all."
+        result = extract_json_from_text(text)
+        assert result is None
+
+    def test_extracts_complex_json(self):
+        """Test extraction of complex JSON."""
+        text = '{"filename": "2024-01-01_Invoice", "tags": ["test", "invoice"], "amount": 100}'
+        result = extract_json_from_text(text)
+        assert '"filename"' in result
+        assert '"tags"' in result