adam-acs/tests/integration/exchange_lifecycle.spec.ts

/**
 * Integration test: Full Exchange Lifecycle
 *
 * Tests the complete flow:
 *   SOAP capture → persist to MongoDB → SSE event emitted → data integrity verified
 *
 * This is a unit-level integration test using mocks (not a real MongoDB connection).
 * We mock the MongoDB layer but verify the data flows through:
 *   ExchangeStoreService → ExchangeModel → EventEmitter correctly.
 *
 * Validates: Requirements 1.1, 1.7, 6.1, 6.2
 */
import { beforeEach, afterEach, describe, expect, it, vi } from 'vitest'

// ─── MongoDB Mocks ──────────────────────────────────────────────────────────────

let sequenceCounter = 0
const mockInsertOne = vi.fn().mockImplementation(async () => ({ insertedId: 'mock-id' }))
const mockCountDocuments = vi.fn().mockResolvedValue(0)
const mockDeleteMany = vi.fn().mockResolvedValue({ deletedCount: 0 })
const mockFind = vi.fn().mockReturnValue({
  sort: vi.fn().mockReturnThis(),
  limit: vi.fn().mockReturnThis(),
  project: vi.fn().mockReturnThis(),
  toArray: vi.fn().mockResolvedValue([]),
})

const mockFindOneAndUpdate = vi.fn().mockImplementation(async () => {
  sequenceCounter++
  return { seq: sequenceCounter }
})

vi.mock('#providers/mongodb_provider', () => ({
  getMongoDb: () => ({
    collection: (name: string) => {
      if (name === 'cwmp_exchange_counters') {
        return { findOneAndUpdate: mockFindOneAndUpdate }
      }
      return {
        insertOne: mockInsertOne,
        countDocuments: mockCountDocuments,
        deleteMany: mockDeleteMany,
        find: mockFind,
        findOne: vi.fn().mockResolvedValue(null),
      }
    },
  }),
}))

vi.mock('#models/exchange', () => ({
  default: {
    collectionName: 'cwmp_exchanges',
    getCollection: () => ({
      insertOne: mockInsertOne,
      countDocuments: mockCountDocuments,
      deleteMany: mockDeleteMany,
      find: mockFind,
      findOne: vi.fn().mockResolvedValue(null),
    }),
    countByDevice: vi.fn().mockResolvedValue(0),
    deleteOldestBeyondCap: vi.fn().mockResolvedValue(undefined),
  },
}))

vi.mock('#config/exchange_store', () => ({
  default: {
    maxMessagesPerDevice: 5000,
    ttlSeconds: 86400,
    sse: {
      inactivityTimeoutMs: 300_000,
      absoluteTimeoutMs: 7_200_000,
      maxConnectionsPerDevice: 5,
      retryIntervalMs: 3000,
    },
    retry: {
      maxAttempts: 3,
      baseDelayMs: 1, // 1ms for fast tests
    },
    featureFlags: {
      persistence: true,
      sseEnabled: true,
      apiSource: 'mongodb',
    },
  },
}))

vi.mock('@adonisjs/core/services/logger', () => ({
  default: {
    warn: vi.fn(),
    error: vi.fn(),
    info: vi.fn(),
    debug: vi.fn(),
  },
}))

import { ExchangeStoreService } from '../../app/services/exchange_store_service.js'
import type { CwmpExchange } from '../../app/models/exchange.js'

// ─── Test Suite ─────────────────────────────────────────────────────────────────

describe('Exchange Lifecycle Integration', () => {
  let service: ExchangeStoreService

  beforeEach(() => {
    vi.clearAllMocks()
    sequenceCounter = 0
    // Reset singleton for clean state
    ;(ExchangeStoreService as any).instance = undefined
    service = ExchangeStoreService.getInstance()
  })

  afterEach(() => {
    ;(ExchangeStoreService as any).instance = undefined
  })

  describe('Full lifecycle: SOAP capture → persist → SSE event', () => {
    it('persists a CPE→ACS Inform and emits SSE event with correct data', async () => {
      const soapXml = `<?xml version="1.0" encoding="UTF-8"?>
<soap-env:Envelope xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:cwmp="urn:dslforum-org:cwmp-1-0">
  <soap-env:Body>
    <cwmp:Inform>
      <DeviceId>
        <Manufacturer>Sagemcom</Manufacturer>
        <OUI>F8B7FF</OUI>
        <ProductClass>Livebox 4</ProductClass>
        <SerialNumber>LB4-TEST-001</SerialNumber>
      </DeviceId>
    </cwmp:Inform>
  </soap-env:Body>
</soap-env:Envelope>`

      const deviceId = 'test-device-001'
      const receivedEvents: CwmpExchange[] = []

      // Subscribe to SSE events before persisting
      const listener = (exchange: CwmpExchange) => {
        receivedEvents.push(exchange)
      }
      service.subscribe(deviceId, listener)

      // Simulate SOAP capture → persist (what CwmpLoggerMiddleware does)
      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: '10.0.0.1:54321->192.168.1.1:8080',
        rawXml: soapXml,
      })

      // Verify persistence result
      expect(result).not.toBeNull()
      expect(result!.deviceId).toBe(deviceId)
      expect(result!.direction).toBe('CPE→ACS')
      expect(result!.cwmpMethod).toBe('Inform')
      expect(result!.rawXml).toBe(soapXml)
      expect(result!.sequenceNumber).toBe(1)
      expect(result!.sessionId).toBe('10.0.0.1:54321->192.168.1.1:8080')
      expect(result!.timestamp).toBeDefined()

      // Verify MongoDB insertOne was called with correct document
      expect(mockInsertOne).toHaveBeenCalledTimes(1)
      const insertedDoc = mockInsertOne.mock.calls[0][0]
      expect(insertedDoc.deviceId).toBe(deviceId)
      expect(insertedDoc.direction).toBe('CPE→ACS')
      expect(insertedDoc.cwmpMethod).toBe('Inform')
      expect(insertedDoc.rawXml).toBe(soapXml)
      expect(insertedDoc.sequenceNumber).toBe(1)

      // Verify SSE event was emitted with the same data
      expect(receivedEvents).toHaveLength(1)
      expect(receivedEvents[0].deviceId).toBe(deviceId)
      expect(receivedEvents[0].direction).toBe('CPE→ACS')
      expect(receivedEvents[0].cwmpMethod).toBe('Inform')
      expect(receivedEvents[0].rawXml).toBe(soapXml)
      expect(receivedEvents[0].sequenceNumber).toBe(1)

      service.unsubscribe(deviceId, listener)
    })

    it('persists an ACS→CPE GetParameterValuesResponse and emits SSE event', async () => {
      const responseXml = `<soap-env:Envelope xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:cwmp="urn:dslforum-org:cwmp-1-0">
  <soap-env:Body>
    <cwmp:GetParameterValuesResponse>
      <ParameterList>
        <ParameterValueStruct>
          <Name>Device.DeviceInfo.SoftwareVersion</Name>
          <Value>SR40_sip-fr-4.62.0</Value>
        </ParameterValueStruct>
      </ParameterList>
    </cwmp:GetParameterValuesResponse>
  </soap-env:Body>
</soap-env:Envelope>`

      const deviceId = 'test-device-002'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)

      service.subscribe(deviceId, listener)

      const result = await service.persistExchange({
        deviceId,
        direction: 'ACS→CPE',
        sessionId: '192.168.1.1:8080->10.0.0.1:54321',
        rawXml: responseXml,
      })

      // Verify data integrity across all steps
      expect(result).not.toBeNull()
      expect(result!.deviceId).toBe(deviceId)
      expect(result!.direction).toBe('ACS→CPE')
      expect(result!.cwmpMethod).toBe('GetParameterValuesResponse')
      expect(result!.rawXml).toBe(responseXml)

      // Verify SSE event matches persisted document
      expect(receivedEvents).toHaveLength(1)
      expect(receivedEvents[0]).toEqual(result)

      service.unsubscribe(deviceId, listener)
    })

    it('handles a complete session: CPE→ACS Inform + ACS→CPE InformResponse', async () => {
      const deviceId = 'test-device-session'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)

      service.subscribe(deviceId, listener)

      // Step 1: CPE sends Inform
      const informXml = `<soap-env:Envelope xmlns:cwmp="urn:dslforum-org:cwmp-1-0">
  <soap-env:Body><cwmp:Inform><DeviceId/></cwmp:Inform></soap-env:Body>
</soap-env:Envelope>`

      const inform = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: '10.0.0.1:5000->192.168.1.1:8080',
        rawXml: informXml,
      })

      // Step 2: ACS responds with InformResponse
      const informResponseXml = `<soap-env:Envelope xmlns:cwmp="urn:dslforum-org:cwmp-1-0">
  <soap-env:Body><cwmp:InformResponse><MaxEnvelopes>1</MaxEnvelopes></cwmp:InformResponse></soap-env:Body>
</soap-env:Envelope>`

      const informResponse = await service.persistExchange({
        deviceId,
        direction: 'ACS→CPE',
        sessionId: '10.0.0.1:5000->192.168.1.1:8080',
        rawXml: informResponseXml,
      })

      // Verify sequence numbers are monotonically increasing
      expect(inform!.sequenceNumber).toBe(1)
      expect(informResponse!.sequenceNumber).toBe(2)

      // Verify all events were emitted in order
      expect(receivedEvents).toHaveLength(2)
      expect(receivedEvents[0].cwmpMethod).toBe('Inform')
      expect(receivedEvents[0].direction).toBe('CPE→ACS')
      expect(receivedEvents[0].sequenceNumber).toBe(1)
      expect(receivedEvents[1].cwmpMethod).toBe('InformResponse')
      expect(receivedEvents[1].direction).toBe('ACS→CPE')
      expect(receivedEvents[1].sequenceNumber).toBe(2)

      // Verify data integrity: rawXml preserved at each step
      expect(receivedEvents[0].rawXml).toBe(informXml)
      expect(receivedEvents[1].rawXml).toBe(informResponseXml)

      service.unsubscribe(deviceId, listener)
    })
  })

  describe('Data integrity verification', () => {
    it('preserves deviceId through the entire lifecycle', async () => {
      const deviceId = 'unique-device-id-αβγ'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)
      service.subscribe(deviceId, listener)

      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 'sess-1',
        rawXml: '<cwmp:Inform/>',
      })

      // Verify deviceId preserved: service return
      expect(result!.deviceId).toBe(deviceId)
      // Verify deviceId preserved: MongoDB insert
      expect(mockInsertOne.mock.calls[0][0].deviceId).toBe(deviceId)
      // Verify deviceId preserved: SSE event
      expect(receivedEvents[0].deviceId).toBe(deviceId)

      service.unsubscribe(deviceId, listener)
    })

    it('preserves direction through the entire lifecycle', async () => {
      const deviceId = 'direction-test'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)
      service.subscribe(deviceId, listener)

      // Test CPE→ACS direction
      await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      // Test ACS→CPE direction
      await service.persistExchange({
        deviceId,
        direction: 'ACS→CPE',
        sessionId: 's1',
        rawXml: '<cwmp:GetParameterValues/>',
      })

      expect(receivedEvents[0].direction).toBe('CPE→ACS')
      expect(receivedEvents[1].direction).toBe('ACS→CPE')

      // Verify in MongoDB writes
      expect(mockInsertOne.mock.calls[0][0].direction).toBe('CPE→ACS')
      expect(mockInsertOne.mock.calls[1][0].direction).toBe('ACS→CPE')

      service.unsubscribe(deviceId, listener)
    })

    it('preserves cwmpMethod extraction through the entire lifecycle', async () => {
      const deviceId = 'method-test'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)
      service.subscribe(deviceId, listener)

      const methods = [
        { xml: '<cwmp:Inform/>', expected: 'Inform' },
        { xml: '<cwmp:GetParameterValues/>', expected: 'GetParameterValues' },
        { xml: '<cwmp:SetParameterValuesResponse/>', expected: 'SetParameterValuesResponse' },
        { xml: '', expected: 'Empty' },
        { xml: '<no-cwmp-here/>', expected: 'Unknown' },
      ]

      for (const { xml } of methods) {
        await service.persistExchange({
          deviceId,
          direction: 'CPE→ACS',
          sessionId: 'sess',
          rawXml: xml,
        })
      }

      // Verify each extracted method in the SSE events
      expect(receivedEvents[0].cwmpMethod).toBe('Inform')
      expect(receivedEvents[1].cwmpMethod).toBe('GetParameterValues')
      expect(receivedEvents[2].cwmpMethod).toBe('SetParameterValuesResponse')
      expect(receivedEvents[3].cwmpMethod).toBe('Empty')
      expect(receivedEvents[4].cwmpMethod).toBe('Unknown')

      // Verify same values in MongoDB inserts
      for (let i = 0; i < methods.length; i++) {
        expect(mockInsertOne.mock.calls[i][0].cwmpMethod).toBe(methods[i].expected)
      }

      service.unsubscribe(deviceId, listener)
    })

    it('preserves rawXml without modification through the entire lifecycle', async () => {
      const deviceId = 'rawxml-test'
      const receivedEvents: CwmpExchange[] = []
      const listener = (exchange: CwmpExchange) => receivedEvents.push(exchange)
      service.subscribe(deviceId, listener)

      const complexXml = `<?xml version="1.0" encoding="UTF-8"?>
<soap-env:Envelope xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:soap-enc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:cwmp="urn:dslforum-org:cwmp-1-0">
  <soap-env:Header>
    <cwmp:ID soap-env:mustUnderstand="1">123456</cwmp:ID>
  </soap-env:Header>
  <soap-env:Body>
    <cwmp:Inform>
      <DeviceId>
        <Manufacturer>Sagemcom</Manufacturer>
        <OUI>F8B7FF</OUI>
        <ProductClass>Livebox 4</ProductClass>
        <SerialNumber>LB4-TEST-001</SerialNumber>
      </DeviceId>
      <Event>
        <EventStruct>
          <EventCode>0 BOOTSTRAP</EventCode>
          <CommandKey></CommandKey>
        </EventStruct>
      </Event>
      <ParameterList>
        <ParameterValueStruct>
          <Name>Device.DeviceInfo.SoftwareVersion</Name>
          <Value xsi:type="xsd:string">4.62.0</Value>
        </ParameterValueStruct>
      </ParameterList>
    </cwmp:Inform>
  </soap-env:Body>
</soap-env:Envelope>`

      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: '10.0.0.1:1234->192.168.1.1:8080',
        rawXml: complexXml,
      })

      // Verify rawXml preserved exactly in service result
      expect(result!.rawXml).toBe(complexXml)
      // Verify rawXml preserved exactly in MongoDB insert
      expect(mockInsertOne.mock.calls[0][0].rawXml).toBe(complexXml)
      // Verify rawXml preserved exactly in SSE event
      expect(receivedEvents[0].rawXml).toBe(complexXml)

      service.unsubscribe(deviceId, listener)
    })
  })

  describe('SSE event emission and subscription', () => {
    it('emits events only to subscribers of the correct device', async () => {
      const eventsA: CwmpExchange[] = []
      const eventsB: CwmpExchange[] = []
      const listenerA = (e: CwmpExchange) => eventsA.push(e)
      const listenerB = (e: CwmpExchange) => eventsB.push(e)

      service.subscribe('device-A', listenerA)
      service.subscribe('device-B', listenerB)

      await service.persistExchange({
        deviceId: 'device-A',
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      expect(eventsA).toHaveLength(1)
      expect(eventsB).toHaveLength(0)

      await service.persistExchange({
        deviceId: 'device-B',
        direction: 'ACS→CPE',
        sessionId: 's2',
        rawXml: '<cwmp:GetParameterValuesResponse/>',
      })

      expect(eventsA).toHaveLength(1)
      expect(eventsB).toHaveLength(1)

      service.unsubscribe('device-A', listenerA)
      service.unsubscribe('device-B', listenerB)
    })

    it('stops emitting after unsubscribe', async () => {
      const deviceId = 'unsub-test'
      const events: CwmpExchange[] = []
      const listener = (e: CwmpExchange) => events.push(e)

      service.subscribe(deviceId, listener)

      await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })
      expect(events).toHaveLength(1)

      service.unsubscribe(deviceId, listener)

      await service.persistExchange({
        deviceId,
        direction: 'ACS→CPE',
        sessionId: 's1',
        rawXml: '<cwmp:InformResponse/>',
      })
      expect(events).toHaveLength(1) // No new event after unsubscribe
    })

    it('supports multiple subscribers for the same device', async () => {
      const deviceId = 'multi-sub'
      const events1: CwmpExchange[] = []
      const events2: CwmpExchange[] = []

      const listener1 = (e: CwmpExchange) => events1.push(e)
      const listener2 = (e: CwmpExchange) => events2.push(e)

      service.subscribe(deviceId, listener1)
      service.subscribe(deviceId, listener2)

      await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      expect(events1).toHaveLength(1)
      expect(events2).toHaveLength(1)
      expect(events1[0]).toEqual(events2[0])

      service.unsubscribe(deviceId, listener1)
      service.unsubscribe(deviceId, listener2)
    })
  })

  describe('Retry behavior for critical vs non-critical messages (Req 1.7)', () => {
    it('retries for critical Inform message on MongoDB failure — never interrupts CWMP', async () => {
      // Reset mock entirely and make all inserts fail
      mockInsertOne.mockReset()
      mockInsertOne.mockRejectedValue(new Error('MongoDB write failed'))

      const deviceId = 'retry-critical-test'
      const events: CwmpExchange[] = []
      const listener = (e: CwmpExchange) => events.push(e)
      service.subscribe(deviceId, listener)

      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      // Service never throws and still returns the exchange (fire-and-forget persistence)
      // The CWMP session must NOT be interrupted regardless of persistence outcome
      expect(result).not.toBeNull()
      expect(result!.cwmpMethod).toBe('Inform')
      expect(result!.deviceId).toBe(deviceId)

      // Verify retries happened: 1 initial attempt + 3 retries = 4 total calls
      expect(mockInsertOne).toHaveBeenCalledTimes(4)

      // SSE event is still emitted (subscribers get notified even on write failure)
      expect(events).toHaveLength(1)
      expect(events[0].cwmpMethod).toBe('Inform')

      service.unsubscribe(deviceId, listener)
    })

    it('does NOT retry for non-critical Empty message on MongoDB failure', async () => {
      // Reset mock entirely and make insert fail
      mockInsertOne.mockReset()
      mockInsertOne.mockRejectedValue(new Error('MongoDB write failed'))

      const deviceId = 'retry-noncritical-test'
      const events: CwmpExchange[] = []
      const listener = (e: CwmpExchange) => events.push(e)
      service.subscribe(deviceId, listener)

      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '', // Empty → non-critical
      })

      // Service still returns exchange (fire-and-forget), CWMP never interrupted
      expect(result).not.toBeNull()
      expect(result!.cwmpMethod).toBe('Empty')

      // Only 1 attempt — non-critical messages are discarded immediately on failure
      expect(mockInsertOne).toHaveBeenCalledTimes(1)

      // SSE event still emitted
      expect(events).toHaveLength(1)

      service.unsubscribe(deviceId, listener)
    })

    it('critical messages get 3 retries while non-critical get 0 retries', async () => {
      // This verifies the retry classification difference:
      // Critical: 1 initial + 3 retries = 4 attempts
      // Non-critical: 1 initial + 0 retries = 1 attempt
      mockInsertOne.mockReset()
      mockInsertOne.mockRejectedValue(new Error('MongoDB down'))

      // Test critical method (Inform)
      await service.persistExchange({
        deviceId: 'retry-class-test',
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })
      const criticalAttempts = mockInsertOne.mock.calls.length
      expect(criticalAttempts).toBe(4) // 1 initial + 3 retries

      // Reset and test non-critical method (Unknown)
      mockInsertOne.mockClear()
      await service.persistExchange({
        deviceId: 'retry-class-test',
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<no-cwmp-element/>',
      })
      const nonCriticalAttempts = mockInsertOne.mock.calls.length
      expect(nonCriticalAttempts).toBe(1) // Only 1 attempt, no retries
    })
  })

  describe('Sequence number assignment (Req 1.1)', () => {
    it('assigns monotonically increasing sequence numbers across multiple messages', async () => {
      const deviceId = 'seq-test'
      const events: CwmpExchange[] = []
      const listener = (e: CwmpExchange) => events.push(e)
      service.subscribe(deviceId, listener)

      for (let i = 0; i < 5; i++) {
        await service.persistExchange({
          deviceId,
          direction: i % 2 === 0 ? 'CPE→ACS' : 'ACS→CPE',
          sessionId: 'sess',
          rawXml: `<cwmp:Inform/>`,
        })
      }

      expect(events).toHaveLength(5)
      for (let i = 0; i < 5; i++) {
        expect(events[i].sequenceNumber).toBe(i + 1)
      }

      // Verify atomic increment was called for each message
      expect(mockFindOneAndUpdate).toHaveBeenCalledTimes(5)

      service.unsubscribe(deviceId, listener)
    })

    it('uses device-scoped sequence numbers (separate counters per device)', async () => {
      const eventsA: CwmpExchange[] = []
      const eventsB: CwmpExchange[] = []
      const listenerA = (e: CwmpExchange) => eventsA.push(e)
      const listenerB = (e: CwmpExchange) => eventsB.push(e)
      service.subscribe('dev-X', listenerA)
      service.subscribe('dev-Y', listenerB)

      await service.persistExchange({
        deviceId: 'dev-X',
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      await service.persistExchange({
        deviceId: 'dev-Y',
        direction: 'CPE→ACS',
        sessionId: 's2',
        rawXml: '<cwmp:Inform/>',
      })

      // Verify the counter collection is called with device-scoped _id
      expect(mockFindOneAndUpdate).toHaveBeenCalledWith(
        { _id: 'dev-X' },
        { $inc: { seq: 1 } },
        { upsert: true, returnDocument: 'after' }
      )
      expect(mockFindOneAndUpdate).toHaveBeenCalledWith(
        { _id: 'dev-Y' },
        { $inc: { seq: 1 } },
        { upsert: true, returnDocument: 'after' }
      )

      service.unsubscribe('dev-X', listenerA)
      service.unsubscribe('dev-Y', listenerB)
    })
  })

  describe('CWMP session non-blocking guarantee', () => {
    it('never throws even if MongoDB sequence counter is unavailable', async () => {
      mockFindOneAndUpdate.mockRejectedValue(new Error('MongoDB unavailable'))

      const deviceId = 'error-test'

      // Should not throw — CWMP session must never be interrupted
      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<cwmp:Inform/>',
      })

      expect(result).toBeNull()
    })

    it('never throws even if MongoDB insertOne is unavailable', async () => {
      mockInsertOne.mockRejectedValue(new Error('MongoDB insertOne failed'))

      const deviceId = 'insert-error-test'

      // Should not throw — returns null
      const result = await service.persistExchange({
        deviceId,
        direction: 'CPE→ACS',
        sessionId: 's1',
        rawXml: '<no-cwmp/>',  // Unknown → non-critical, no retries
      })

      expect(result).toBeNull()
    })
  })
})