fix(test): make the ciphertext-tamper test deterministic - #302
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telivity-otaip merged 1 commit intoAug 11, 2026
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replace(/a/g,'b') on random hex ciphertext is a no-op whenever it contains no
'a' — the blob arrives untampered and the test fails claiming fail-closed is
broken. Flipping to uppercase 'A' has the same bug (hex 'A'==='a'). Change the
first hex DIGIT ('0'<->'1') instead: distinct nibble values, bytes always
change, verified across all 16 possible first digits.
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Nice catch on the flaky tamper — replace(/a/g,'b') is a no-op when the hex has no a. Deterministic first-nibble flip is exactly right. Thank you, Charles — merging.
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`credential-encryption.spec.ts` › "fails closed when ciphertext is tampered" is probabilistically flaky: it tampers with `blob.ciphertext.replace(/a/g, 'b')`, and whenever the random ciphertext contains no `a`, the replacement is a no-op — the blob arrives untampered, decryption rightly succeeds, and the test fails claiming fail-closed is broken.
Hit tonight in our CI: `1 failed | 1411 passed` on a branch touching none of this code, with the identical tree passing minutes earlier.
Fix: flip the first character to a guaranteed-different one. Same intent, zero probability.
(The auth-tag test above it is already deterministic — `'0'.repeat(...)` can collide with an all-zero tag only with negligible probability, so left alone.)