test: cover StreamingQueue batching

web/src/utils/__tests__/streaming-queue.test.ts

@@ -0,0 +1,103 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { StreamingQueue } from '../streaming-queue'
+
+describe('StreamingQueue', () => {
+  let rafCallbacks: FrameRequestCallback[]
+  let nextRafId: number
+  let cancelledRafIds: number[]
+
+  beforeEach(() => {
+    rafCallbacks = []
+    nextRafId = 1
+    cancelledRafIds = []
+
+    vi.stubGlobal(
+      'requestAnimationFrame',
+      vi.fn((callback: FrameRequestCallback) => {
+        rafCallbacks.push(callback)
+        return nextRafId++
+      }),
+    )
+
+    vi.stubGlobal(
+      'cancelAnimationFrame',
+      vi.fn((id: number) => {
+        cancelledRafIds.push(id)
+      }),
+    )
+  })
+
+  afterEach(() => {
+    vi.unstubAllGlobals()
+  })
+
+  it('queues items and flushNow delivers accumulated content', () => {
+    const callback = vi.fn()
+    const queue = new StreamingQueue(callback)
+
+    queue.add('message-1', 'Hel')
+    queue.add('message-1', 'lo')
+    queue.flushNow()
+
+    expect(callback).toHaveBeenCalledTimes(1)
+    expect(callback).toHaveBeenCalledWith('message-1', 'Hello')
+    expect(cancelAnimationFrame).toHaveBeenCalledWith(1)
+    expect(cancelledRafIds).toEqual([1])
+  })
+
+  it('batches multiple keys before a flush', () => {
+    const callback = vi.fn()
+    const queue = new StreamingQueue(callback)
+
+    queue.add('first', 'A')
+    queue.add('second', 'B')
+    queue.add('first', 'C')
+
+    expect(requestAnimationFrame).toHaveBeenCalledTimes(1)
+
+    queue.flushNow()
+
+    expect(callback).toHaveBeenCalledTimes(2)
+    expect(callback).toHaveBeenNthCalledWith(1, 'first', 'AC')
+    expect(callback).toHaveBeenNthCalledWith(2, 'second', 'B')
+  })
+
+  it('flushNow is a no-op when the queue is empty', () => {
+    const callback = vi.fn()
+    const queue = new StreamingQueue(callback)
+
+    queue.flushNow()
+
+    expect(callback).not.toHaveBeenCalled()
+    expect(cancelAnimationFrame).not.toHaveBeenCalled()
+  })
+
+  it('flushes from the scheduled requestAnimationFrame callback', () => {
+    const callback = vi.fn()
+    const queue = new StreamingQueue(callback)
+
+    queue.add('message-1', 'Hi')
+
+    expect(callback).not.toHaveBeenCalled()
+    expect(rafCallbacks).toHaveLength(1)
+
+    rafCallbacks[0](16)
+
+    expect(callback).toHaveBeenCalledOnce()
+    expect(callback).toHaveBeenCalledWith('message-1', 'Hi')
+  })
+
+  it('destroy cancels pending work and ignores future adds', () => {
+    const callback = vi.fn()
+    const queue = new StreamingQueue(callback)
+
+    queue.add('message-1', 'pending')
+    queue.destroy()
+    queue.add('message-1', 'ignored')
+    queue.flushNow()
+
+    expect(callback).not.toHaveBeenCalled()
+    expect(cancelAnimationFrame).toHaveBeenCalledWith(1)
+    expect(requestAnimationFrame).toHaveBeenCalledTimes(1)
+  })
+})