My Python tests passed. Production still broke.

My Python tests passed. Production still broke. Pushed a fix to production Friday afternoon. All 47 unit tests green. Felt good about it. Monday morning: 200+ error logs. The code worked fine in tests but crashed on real data. What happened Built a data parser that cleaned product prices from scraped HTML. Test suite covered edge cases. Empty strings, None values, malformed numbers. Everything passed locally. Production data had something my tests never checked: Unicode characters mixed with numbers. $19.⁹⁹ instead of $19.99 . The superscript 9s came from copying prices that had footnote markers. My regex assumed normal digits. # What I tested def clean_price ( text ): if not text : return 0.0 match = re . search ( r ' \d+\.?\d* ' , text ) return float ( match . group ()) if match else 0.0 # Test that passed assert clean_price ( " $19.99 " ) == 19.99 assert clean_price ( "" ) == 0.0 assert clean_price ( None ) == 0.0 The regex matched 19. and stopped at the superscript 9. Converted to