Claude Opus writes 10 unit tests for a constant string, sparking the 'no tautological tests' rule

mattpocockuk · x · 2026-09-22

Developer dexhorthy shared how Claude Opus added 10 unit tests verifying that a constant string contains various substrings — testing a literal that can never change. TypeScript educator Matt Pocock quote-shared with a one-line test guideline: "No tautological tests."

It's a textbook AI coding-agent failure mode: optimizing for coverage rather than for verifying actual behavior.

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