Cross-Check
Four overlapping checks, each part in a unique combination; change the thing; the failing pattern names the part; fix only that.
Formerly Syndrome
Hamming code: the failed parity bits spell the flipped bit’s address.
Seen in Arthur Wynne, the "word-cross", New York World, 21 December 1913
Try it on your work
Before you change the thing you're working on, define four checks that overlap, each covering a different half of its parts, so that every part is in a unique combination of checks. Change it. Run the checks. Stop when the pattern of failures names one part. Fix only that part.
Write four one-line tests your project's description must pass, each testing an overlapping set of sentences. Revise the description. Run the tests. Stop when the failing set points to one sentence; that is the one that broke.
Set up three overlapping reviews of your process, each covering some steps and not others, so that each step has a unique signature. When something goes wrong, read which reviews flagged it. Stop when the signature identifies the step without an investigation.
How it has been used
Error-correcting codes add overlapping parity checks to data. When a bit changes, the checks that fail form a “syndrome”: a compact pattern that identifies the corrupted position and can guide correction. Spacecraft and deep-space communication use error-correcting codes because asking for a clean retransmission may be slow, costly or impossible.
Where it leads
Grouped under Let me find out what holds up