I built a medical record parser that passed code review and every synthetic test in the suite. Then I ran five actual patient portal exports through it.
Two bugs emerged instantly. The first: self-closing XML tags like `<birthTime value="19811023" />` were stripping the forward slash in the closing syntax, erasing the date entirely. The second: a boundary query meant to read encounter dates was instead capturing every temporal marker in the file, creating a care span of 1981 to 2099. Both would have shipped silent. Both would have corrupted downstream care planning, outcome tracking, safety alerts—every system built on that data.
The parser now halts loud. It reads deterministically or it refuses to move the record. And it only validates against real portal data, never fixtures. Code review cannot see what real data reveals.
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