# `testing.FakeSession.resize`

> Contract 2.0.0 · package sha256 `a857eca95b35921109faf997094bb4192f12527d9d0fcd4be7e97f06425bad6e` · generated from `testing.d.ts` by `services/onsite-scripter/scripts/build-contract-docs.mjs`; edit the source, not this file.

Method of [`testing.FakeSession`](testing.FakeSession.md) · labs, `@experimental` · since 2.0.0 · optional: reach it through `has()`

```ts
resize?(width: number, height: number): void;
```

Resizes the element to `width` × `height` CSS px, as the page's layout would: the viewport
`createFakeSession` took changes at once ([`camera.state.aspect`](CameraState.aspect.md), [`camera.project`](Camera.project.md), picks,
[`info()`](Session.info.md)), 'resize' fires at the next drawn frame with the new size, and the anchors report
again after it ('anchors:moved'). The same size again does nothing.
Errors: a width or height that is not a positive finite number throws HoloInputError.
Experimental, so optional in this declaration: a test calls `fake.resize?.(w, h)`.

## Example

Imports: values (`has`, `validate`, the `Holo*Error` classes, the pure helpers) from `@holostep-configurators/runtime-client`, types from `@holostep-configurators/runtime-client/contract`, `/math` and `/testing` names from those entries; `boot` from the runtime module the root's `loadRuntimeAtFloor` resolves to. A type your page defines is your app's: declare it there, never import it from the package.

Compiled under the contract's strict settings (`examples/declaration/24-FakeSession.resize.ts`):

```ts
import { createFakeSession } from '@holostep-configurators/runtime-client/testing';
import type { Session } from '@holostep-configurators/runtime-client/contract';
declare const session: Session;
declare const signal: AbortSignal;
// A layout that switches to its narrow panel under 600 CSS px.
const fake = createFakeSession({ viewport: { width: 800, height: 600 } });
export const layout = { narrow: false };
fake.on('resize', ({ width }) => void (layout.narrow = width < 600));
fake.resize?.(390, 700);
fake.tick(16);                                            // 'resize' { width: 390, height: 700 }
if (!layout.narrow) throw new Error('the narrow layout did not switch on');
```

## Generic-API test (spec 3.1)

| Rule | Result |
| --- | --- |
| 1. Neutral name | pass: `resize` names no product |
| 2. A precedent | not recorded: no ledger row (coverage.json) names this member or its owner |
| 3. Two apps, or labs | labs (`@experimental` at a stable path, reached through `has()` or `supports()`): it graduates when a second app uses it |
| 4. The cheaper fix first | not recorded per member (Appendix B decides it per need) |