test(ui): проверить поздний фрагмент открытого потока

tests/e2e/traffic-flow.spec.ts

@@ -222,3 +222,66 @@ test('Flow: смена сервера отменяет старую SSE-подп
   await expect(page.getByText('SSE текущего сервера', { exact: true }).filter({ visible: true })).toBeVisible()
   await expect(page.getByLabel('Скорость потоков')).toContainText('7.00 Мбит/с')
 })
+
+test('Flow: позднее чтение открытого SSE не заменяет данные нового сервера', async ({ page }) => {
+  await setup(page)
+  await page.getByRole('button', { name: '15м', exact: true }).click()
+  await expect(page.getByText('Категория 15m', { exact: true }).filter({ visible: true })).toBeVisible()
+  // Deliberately let the mock stream deliver a chunk after abort. This exercises
+  // the post-read guard, independently of the browser transport's cancellation.
+  await page.evaluate(() => {
+    const originalFetch = window.fetch.bind(window)
+    const state = { pending: false, aborted: false, delivered: false, release: () => {} }
+    Object.assign(window, { delayedFlowStream: state })
+    window.fetch = async (input, init) => {
+      const url = new URL(input instanceof Request ? input.url : String(input), location.href)
+      if (url.pathname !== '/api/traffic/flow/live') return originalFetch(input, init)
+      const old = url.searchParams.get('serverId') === '1'
+      const sample = (late = false) => ({
+        bpsNow: old ? (late ? 99000000 : 1000000) : 7000000,
+        bytes: 200, packets: 2, conversations: 1, uniqueSrc: 1, uniqueDst: 1,
+        topProto: 'TCP', topCategory: old ? (late ? 'Поздний фрагмент' : 'Открытый поток первого') : 'Открытый поток второго',
+        rxSeries: [1], txSeries: [2], applications: [], protocols: [], sources: [],
+        destinations: [], interfaces: [], conversationsList: [], ifaces: [], live: true,
+      })
+      const encode = (late = false) => new TextEncoder().encode('event: sample\ndata: ' + JSON.stringify(sample(late)) + '\n\n')
+      const stream = new ReadableStream<Uint8Array>({
+        start(controller) {
+          controller.enqueue(encode())
+          if (old) state.release = () => controller.enqueue(encode(true))
+        },
+      })
+      const response = new Response(stream, { headers: { 'Content-Type': 'text/event-stream' } })
+      if (old) {
+        init?.signal?.addEventListener('abort', () => { state.aborted = true })
+        const reader = stream.getReader()
+        const read = reader.read.bind(reader)
+        let calls = 0
+        reader.read = async () => {
+          const delayed = ++calls === 2
+          if (delayed) state.pending = true
+          const result = await read()
+          if (delayed) { state.pending = false; state.delivered = true }
+          return result
+        }
+        stream.getReader = (() => reader) as typeof stream.getReader
+      }
+      return response
+    }
+  })
+  await page.getByRole('button', { name: '5м', exact: true }).click()
+  await expect(page.getByText('Открытый поток первого', { exact: true }).filter({ visible: true })).toBeVisible()
+  const streamState = () => page.evaluate(() => {
+    const state = (window as unknown as { delayedFlowStream: { pending: boolean; aborted: boolean; delivered: boolean } }).delayedFlowStream
+    return { pending: state.pending, aborted: state.aborted, delivered: state.delivered }
+  })
+  await expect.poll(streamState).toEqual({ pending: true, aborted: false, delivered: false })
+  await page.getByRole('button').filter({ hasText: 'Экспортёр второй' }).click()
+  await expect(page.getByText('Открытый поток второго', { exact: true }).filter({ visible: true })).toBeVisible()
+  await expect.poll(streamState).toEqual({ pending: true, aborted: true, delivered: false })
+  await page.evaluate(() => (window as unknown as { delayedFlowStream: { release: () => void } }).delayedFlowStream.release())
+  await expect.poll(streamState).toEqual({ pending: false, aborted: true, delivered: true })
+  await expect(page.getByText('Поздний фрагмент', { exact: true })).toHaveCount(0)
+  await expect(page.getByText('Открытый поток второго', { exact: true }).filter({ visible: true })).toBeVisible()
+  await expect(page.getByLabel('Скорость потоков')).toContainText('7.00 Мбит/с')
+})