hardDesignCase StudySeniorStaffLead
You are reusing a component that has run without incident for years in another product. What does your test strategy have to say about it?
6 min readUpdated 2026-08-15Target archetype: Big Tech, Enterprise Captive, Product Startup
Answer
Short answer
A clean track record is evidence about the old system's operating envelope, not about yours, so the strategy must surface the assumptions the component inherits, test it against the new envelope rather than trusting its history, and state which inherited assumptions are going untested.
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Likely follow-ups
- The component has no tests of its own and everyone who wrote it has left. Where do you start?
- How do you test for a failure mode that is silent rather than a crash?
- The component is a third-party library rather than internal code. What changes about your approach?
- What would you write down so the next team to reuse it does not repeat this?
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