Silent Hypotheses in Generated Code

Problem

Passing tests prove only that the code behaves correctly on the cases the tests cover, which are usually the cases that share the same unstated premise the code was written under. The hidden assumption is therefore invisible at exactly the two moments meant to catch defects: the green suite confirms the happy path the model already assumed, and the reviewer, reading fluent code, sees no flag because nothing names the premise. The assumption surfaces only when production sends an input that violates it, and by then the failure looks like a runtime incident with no obvious cause rather than a design choice nobody made on purpose.

Solution

The remedy is to treat passing tests as non-proof of correctness and to surface the hidden premises before they ship. When generating code, have the model emit the assumptions it made explicit alongside the code as comments, preconditions, or assertions, so every silent default becomes a named, reviewable claim. Add tests that target the violated-premise cases — empty inputs, unsorted data, foreign currency, late upstream responses — rather than only the happy path the code was written under. In review, ask of each change what it assumes about its inputs and environment and whether anything checks that assumption, treating an unnamed premise as a defect rather than a detail. Where a premise cannot be tested cheaply, encode it as a runtime guard that fails loudly instead of corrupting state quietly.

When to use

• A team relies on a model or coding agent to generate or modify code that ships to production.
• Generated changes are gated mainly by a passing test suite and a quick human review.
• Prompts often leave input shapes, environment, or edge cases unspecified, so the model must fill them with defaults.