@johngw/stream/test/transformers/flat.test.ts

Reactive programming tools using the WHATWG Streams API.

import { timeout } from '@johngw/stream-common'
import { fromTimeline } from '@johngw/stream-jest'
import { fromCollection } from '@johngw/stream/sources/fromCollection'
import { flat } from '@johngw/stream/transformers/flat'

test('flattens iterables', async () => {
  await expect(
    fromTimeline(`
    -[1,2]-[3,[[4]]]-|
    `).pipeThrough(flat<number[]>())
  ).toMatchTimeline(`
    -1-2---3-4-------|
  `)
})

test('flattens async iterables', async () => {
  await expect(
    fromCollection([
      (async function* () {
        yield 1
        await timeout(1)
        yield 2
      })(),
      (async function* () {
        yield 3
        await timeout(1)
        yield (async function* () {
          await timeout(1)
          yield 4
        })()
      })(),
    ]).pipeThrough(flat())
  ).toMatchTimeline(`
    -1-2-3-4-
  `)
})

test('flattens array likes', async () => {
  await expect(
    fromCollection({ 0: 'zero', 1: 'one', 2: 'three', length: 3 }).pipeThrough(
      flat()
    )
  ).toMatchTimeline(`
    -zero-one-three-
  `)
})

test('queues things that arent iterable', async () => {
  await expect(
    fromTimeline(`
    --{foo: bar}--|
    `).pipeThrough(flat<Record<string, string>>())
  ).toMatchTimeline(`
    --{foo: bar}--
  `)
})

test('flattens a mixture of all iterables things', async () => {
  await expect(
    fromCollection([
      [
        (async function* () {
          yield 1
          await timeout(1)
          yield [2, 3]
        })(),
        (async function* () {
          yield [{ 0: 'zero', length: 1 }]
        })(),
      ],
    ]).pipeThrough(flat())
  ).toMatchTimeline(`
    -1-2-3-zero-
  `)
})