# `testing.FakeSession.script`

> 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) · stable · since 2.0.0

```ts
script(member: string, result: {
  fail?: boolean;
  delayMs?: number;
  problem?: ProblemCode;
  collection?: string;
  cancel?: boolean;
}): void;
```

Forces a member's next outcome, e.g. a load failure. `member` is named as [`TraceEntry.member`](testing.TraceEntry.member.md)
names it ('session.setSceneModel', 'collection.set', 'part.set'), and its next call through
any writer and any handle of that kind is forced, unless [`collection`](Writer.collection.md) names one.
'runtime.input' forces the next drag release's runtime commit and 'runtime.restore' the next
'restore' commit; their only row is 'sync-failed', their default `problem`. With `fail`,
`problem` picks the spec's section 6.4 row:
'sync-failed' is the internal-failure row (a state write rolls back with reason
'internal-error'; a 'collection.load' resolves, then its commit drops the item),
'asset-failed' the asset rows (a declarative write commits without it, an
imperative load rejects HoloAssetError): every asset that write fetches fails once, assets
already loaded stay drawn, and no failure window starts. A failure
that records no Problem takes its row's error: [`session.capture`](Session.capture.md) rejects DOMException
'EncodingError'. 'session.applyDocument' has one row, 'apply-failed' (its default
`problem`): it resolves `ok: false` with one 'apply-failed' problem, and `delayMs` holds the
apply unfinished, so a newer apply supersedes it or a `signal` aborts it.
'session.activateAR' has two rows; neither records a Problem. A failed launch (`fail`, no
`problem`) is timed as the viewer the call opens (spec section 5.11): for Scene Viewer, with
`delayMs` under 2000 it resolves `{ launched: false, reason: 'error' }` with 'ar:status'
'error' then, else it resolves `launched: true` at 2000 ms and fires 'ar:status' 'error' at
`delayMs`; for the in-page route ('webxr') it resolves 'error' at `delayMs`; for Quick Look,
which fails only when its USDZ export does, it resolves 'error' at `delayMs` with that
message ('the USDZ export failed'). A cancel (`cancel: true`) resolves
`{ launched: false, reason: 'cancelled' }` at `delayMs` with 'ar:status' 'error', as the
in-page route answers a declined prompt or a close before the start; Scene Viewer and
Quick Look report no cancel, so a call that opens one of them resolves `launched: true` at
`delayMs` instead. `delayMs` alone holds the launch, and a call meanwhile returns the
pending call's Promise. As on the runtime, [`destroy()`](Session.destroy.md) and `detach()` reject a held launch
with AbortError and close an open [`tryOn()`](Session.tryOn.md) (it resolves at once), and [`endAR()`](Session.endAR.md) resolves a
held in-page launch `{ launched: false, reason: 'cancelled' }` with 'ar:status' 'error'.
A `problem` the member has no row for throws HoloInputError at this call.

## Generic-API test (spec 3.1)

| Rule | Result |
| --- | --- |
| 1. Neutral name | pass: `script` names no product |
| 2. A precedent | not recorded: no ledger row (coverage.json) names this member or its owner |
| 3. Two apps, or labs | not recorded: no ledger row names this member or its owner |
| 4. The cheaper fix first | not recorded per member (Appendix B decides it per need) |