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The Tests Got a Contract Before They Got Code

An agent wrote preconditions, postconditions and undefined behavior before generating a test suite.

Published Updated Story ID: mp-2026-08-19-019
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Summary

An agent wrote preconditions, postconditions and undefined behavior before generating a test suite.

On production bugs from Google, spec-driven generation improved bug detection by 9.8 percentage points and branch coverage by 2.5 points over the direct agent baseline. An LLM judge also preferred many generated suites, a result that complements but does not replace executable bug and coverage measurements.

Why it matters

An agent wrote preconditions, postconditions and undefined behavior before generating a test suite.

Limits and context

  • An LLM judge also preferred many generated suites, a result that complements but does not replace executable bug and coverage measurements.

Key claims

  1. An agent wrote preconditions, postconditions and undefined behavior before generating a test suite.

    Qualification: An LLM judge also preferred many generated suites, a result that complements but does not replace executable bug and coverage measurements.

    Evidence: source-2026-08-19-021

Sources

  1. arXiv preprint 2608.17177arXiv · primary research

Corrections

No corrections have been recorded for this story.