test(ui): проверить трафик после смены источника данных

tests/e2e/backend-switch.e2e.ts

@@ -54,3 +54,52 @@ for (const status of [200, 500]) {
     await expect(page.getByRole('button', { name: 'Новая проба', exact: true })).toBeEnabled()
   })
 }
+
+test('смена backend: поздний список трафика не заменяет новый источник', async ({ page }) => {
+  let hold = false
+  let release!: () => void
+  const gate = new Promise<void>(resolve => { release = resolve })
+  const refreshOrigins: string[] = []
+  await page.route('**/health', route => route.fulfill({ json: { ok: true } }))
+  await page.route('**/api/**', async route => {
+    const url = new URL(route.request().url())
+    const isNew = url.port === '8999'
+    const server = { id: '1', name: isNew ? 'Новый трафик' : 'Старый трафик', site: 'TEST', country: 'RU', status: 'online', rxNow: 2, txNow: 3, rxPeak: 4, txPeak: 5, rxTotal: 100, txTotal: 200, sessions: 1, rxSeries: [1, 2], txSeries: [2, 3] }
+    if (url.pathname === '/api/traffic/servers') {
+      if (hold) {
+        refreshOrigins.push(url.origin)
+        if (!isNew) await gate
+      }
+      return route.fulfill({ json: { servers: [server] } })
+    }
+    const json = url.pathname === '/api/auth/config' ? { required: false }
+      : url.pathname === '/api/traffic/servers/1' ? { server }
+      : url.pathname.endsWith('/interfaces') || url.pathname === '/api/traffic/bound-interfaces' ? { interfaces: [] }
+      : url.pathname === '/api/traffic/users' ? { users: [] }
+      : url.pathname === '/api/servers' ? [] : {}
+    if (url.pathname.endsWith('/live')) return route.fulfill({ status: 503, json: {} })
+    return route.fulfill({ json })
+  })
+  await page.goto('/traffic')
+  await expect(page.getByRole('heading', { name: 'Старый трафик', exact: true })).toBeVisible()
+  hold = true
+  const started = page.waitForRequest(r => r.url().includes(':8000/api/traffic/servers?'))
+  await page.getByRole('button', { name: 'Обновить', exact: true }).click()
+  await started
+  await page.locator('a[href="/settings"]').first().click()
+  const backend = page.getByPlaceholder('http://localhost:8000', { exact: true })
+  await backend.fill('http://127.0.0.1:8999')
+  await backend.press('Enter')
+  await page.goBack()
+  await expect(page.getByRole('heading', { name: 'Новый трафик', exact: true })).toBeVisible()
+  const late = page.waitForResponse(r => r.url().includes(':8000/api/traffic/servers?'))
+  release()
+  await late
+  await expect(page.getByRole('heading', { name: 'Новый трафик', exact: true })).toBeVisible()
+  await expect(page.getByRole('button').filter({ hasText: 'Старый трафик' })).toHaveCount(0)
+  const beforeRefresh = refreshOrigins.length
+  const fresh = page.waitForResponse(r => r.url().includes(':8999/api/traffic/servers?'))
+  await page.getByRole('button', { name: 'Обновить', exact: true }).click()
+  await fresh
+  expect(refreshOrigins.slice(beforeRefresh)).toEqual(['http://127.0.0.1:8999'])
+})