---
url: https://lit-ui-router.dev/api/lit-ui-router-ssr/testing.md
---
[lit-ui-router-ssr](../index.md) / testing

# testing

Measures the hydration round trip: stamp the elements a prerender served
before the client boots, then count how many the boot kept.

No imports, and each function is self-contained, so `String(stampServed)`
and `String(countRetained)` are valid source for a browser page (Playwright's
`page.addInitScript`) as well as plain calls in happy-dom or jsdom.

## Interfaces

* [RetainedCount](interfaces/RetainedCount.md)
* [ServedStamp](interfaces/ServedStamp.md)

## Functions

* [countRetained](functions/countRetained.md)
* [stampServed](functions/stampServed.md)