# Reflect.8. Testing the boundary — Mercury LMS

> Contract: `@fiberfx/reflect` 4.1.1; Hypergraph and Hyperscript 4.1.1.

## Fixture promise

Left +2, right +1, reset left → left 0, right 1, global 0. Browser clicks and DOM assertions; cleanup before dispose. Use @fiberfx/testing render/act/cleanup; container-bound queries. Native mx test supplies the vitest import through its own test runtime.

## Verification status

The chapter supplies an adaptable regression recipe, not a fresh passing-run claim. Run mx test in a configured module with compatible resolved dependencies and Chromium. Missing browser/import, zero tests or missing results is not success. TypeScript checks are separate.

## Falsification

Temporarily share one scope in an isolated fixture: count expectations must fail. Restore isolation. Add runtime duplicate-key/overlap refusals and separate wrong-payload/missing-prop type negatives. Never weaken expectations to accept the failure.

## Transfer

Check projection suppression, keyed DOM/local state, removal cleanup, constructor changes, stable refs, scoped SSR and hook silence. Built-package evidence remains separate from workspace tests. [Manual lab](/examples/reflect-lab/index.html?part=testing&lang=en).

## Source

Reflect collections.test.ts/types.ts, Testing render.ts/index.ts, mx native test runner; Reflect npm 4.1.1.

## Navigation

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