Testing Against State Drift: Guarding a Config Tool Whose Source of Truth Lives Somewhere Else

Short summary

A detailed testing strategy for a browser-based config tool for ESA's Pyxel detector-simulation framework, where correctness depends on an independently-versioned external project. The author identifies three drift layers — bundled schema freshness, argument bounds, and doc accuracy — and builds automated defenses at each seam where the invariant actually lives, including live schema diffs and API introspection checks in CI.

• •Three drift layers: bundled schema freshness, argument bounds, and tutorial/doc accuracy
• •Test each invariant at the seam where it lives — reach for the real external thing at test time
• •CI coverage gates make testing non-optional by blocking merges on untested files

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