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Testing observable queries

ObservableQueryScenario opens a live query through the real observable pipeline and collects what it emits, within a deadline you set.

Collect emissions

The Tasks sample spec registers a task and collects the current value:

import { given } from '@cratis/arc.testing';
import { TaskId } from '../../../TaskId.js';
import { TaskTitle } from '../../../TaskTitle.js';
import { a_task_listing } from '../given/a_task_listing.js';

describe('when collecting the current tasks emission', given(a_task_listing, context => {
    let result: Awaited<ReturnType<typeof context.observable.collect>>;
    beforeEach(async () => {
        context.tasks.register(TaskId.create(), new TaskTitle('Review changes'));
        result = await context.observable.collect(1, 1_000);
    });
    afterAll(async () => { await context.query.dispose(); await context.observable.dispose(); });
    it('should receive the wire-shaped current value', () => {
        result.emissions.should.have.lengthOf(1);
        String(result.emissions[0]?.data?.[0]?.title).should.equal('Review changes');
    });
}));

The a_task_listing context is shown on Testing queries.

collect()

collect(count, timeoutMs = 5000, arguments = {}, options?) waits for up to count emissions, or fails at the deadline, which also covers opening the subscription. The scenario closes its subscription in every case, including a timeout.

Result field	Meaning
`emissions`	The query results received, wire-shaped
`completed`	`true` only when a finite stream completed before reaching `count`
`rejection`	The query result when opening was rejected, such as a failed authorization or validation

A rejection is reported in rejection with completed: false, not as an emission. Always assert the expected emission count.