test: add comprehensive unit tests for generate_fingerprint

Add `src/tests/test_fingerprint.py` to cover:
- Happy path fingerprint generation.
- Custom fingerprint length.
- Input normalization (whitespace/case).
- Error handling via mocked exception in `hashlib.sha256`.
- Invalid input handling (NoneType).

This addresses the gap where the exception path in `src/utils/fingerprint.py` was unreachable with standard inputs.

Co-authored-by: PR0M3TH3AN <[email protected]>

src/tests/test_fingerprint.py

@@ -0,0 +1,64 @@
+import sys
+import logging
+from unittest.mock import patch
+from pathlib import Path
+import pytest
+
+sys.path.append(str(Path(__file__).resolve().parents[1]))
+
+from utils.fingerprint import generate_fingerprint
+
+# Sample seed for testing
+TEST_SEED = "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"
+EXPECTED_FINGERPRINT = "C557EEC878DFD852"
+
+
+def test_generate_fingerprint_valid():
+    """Test standard successful fingerprint generation."""
+    fp = generate_fingerprint(TEST_SEED)
+    assert fp is not None
+    assert len(fp) == 16
+    assert fp.isupper()
+    assert fp == EXPECTED_FINGERPRINT
+
+
+def test_generate_fingerprint_custom_length():
+    """Test fingerprint generation with custom length."""
+    length = 8
+    fp = generate_fingerprint(TEST_SEED, length=length)
+    assert fp is not None
+    assert len(fp) == length
+    assert fp == EXPECTED_FINGERPRINT[:length]
+
+
+def test_generate_fingerprint_normalization():
+    """Test that input is normalized (stripped and lowercased)."""
+    messy_seed = "  " + TEST_SEED.upper() + "  "
+    fp = generate_fingerprint(messy_seed)
+    assert fp == EXPECTED_FINGERPRINT
+
+
+def test_generate_fingerprint_error_handling(caplog):
+    """Test error handling when an exception occurs during generation."""
+    # Patch hashlib.sha256 to raise an exception
+    with patch("hashlib.sha256", side_effect=Exception("Mocked hashing error")):
+        # Ensure we capture logs at ERROR level
+        with caplog.at_level(logging.ERROR):
+            fp = generate_fingerprint(TEST_SEED)
+
+            # Function should return None on error
+            assert fp is None
+
+            # Check that the error was logged
+            assert "Failed to generate fingerprint: Mocked hashing error" in caplog.text
+
+
+def test_generate_fingerprint_invalid_input(caplog):
+    """Test handling of invalid input type which raises AttributeError on .strip()."""
+    with caplog.at_level(logging.ERROR):
+        # Passing None will cause AttributeError: 'NoneType' object has no attribute 'strip'
+        fp = generate_fingerprint(None)
+
+        assert fp is None
+        assert "Failed to generate fingerprint" in caplog.text
+        assert "'NoneType' object has no attribute 'strip'" in caplog.text