Dev Tools · 1h ago
Demo Script Exposes Production Bug Hidden by Green Test Suite
A developer's demo script failed on first run, revealing a production bug in an MCP server that validates tool arguments locally against a hardcoded set of four thinking levels, while the live API only accepts two. The bug caused every live call using the default 'medium' level to fail silently. The incident cost ten minutes to fix but exposed a gap in test coverage against remote APIs.
Meridian48 take
The story underscores how mocked tests can create false confidence, but the bug itself is a minor validation mismatch — not a systemic failure.
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My Demo Script Found a Production Bug on Its First Run: A Tiny Post-Mortem →
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testingapi-validation