diff --git a/src/main/services/__tests__/VolcengineService.test.ts b/src/main/services/__tests__/VolcengineService.test.ts
new file mode 100644
index 0000000000..a724121ba8
--- /dev/null
+++ b/src/main/services/__tests__/VolcengineService.test.ts
@@ -0,0 +1,863 @@
+import crypto from 'crypto'
+import fs from 'fs'
+import path from 'path'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+// Mock dependencies
+vi.mock('@logger', () => ({
+  loggerService: {
+    withContext: () => ({
+      info: vi.fn(),
+      error: vi.fn(),
+      warn: vi.fn(),
+      debug: vi.fn()
+    })
+  }
+}))
+
+vi.mock('electron', () => ({
+  app: {
+    getPath: vi.fn(() => '/test/userData')
+  },
+  safeStorage: {
+    isEncryptionAvailable: vi.fn(() => true),
+    encryptString: vi.fn((str: string) => Buffer.from(`encrypted:${str}`)),
+    decryptString: vi.fn((buffer: Buffer) => {
+      const str = buffer.toString()
+      if (str.startsWith('encrypted:')) {
+        return str.substring('encrypted:'.length)
+      }
+      throw new Error('Invalid encrypted data')
+    })
+  },
+  net: {
+    fetch: vi.fn()
+  }
+}))
+
+vi.mock('@main/utils/file', () => ({
+  getConfigDir: vi.fn(() => '/test/config')
+}))
+
+// Import after mocks
+import { app, net, safeStorage } from 'electron'
+import VolcengineService from '../VolcengineService'
+
+// Access private methods through type assertion for testing
+type VolcengineServiceType = typeof VolcengineService & {
+  sha256Hash(data: string | Buffer): string
+  hmacSha256(key: Buffer | string, data: string): Buffer
+  hmacSha256Hex(key: Buffer | string, data: string): string
+  uriEncode(str: string, encodeSlash?: boolean): string
+  buildCanonicalQueryString(query: Record<string, string>): string
+  buildCanonicalHeaders(headers: Record<string, string>): {
+    canonicalHeaders: string
+    signedHeaders: string
+  }
+  deriveSigningKey(secretKey: string, date: string, region: string, service: string): Buffer
+  createCanonicalRequest(
+    method: string,
+    canonicalUri: string,
+    canonicalQueryString: string,
+    canonicalHeaders: string,
+    signedHeaders: string,
+    payloadHash: string
+  ): string
+  createStringToSign(dateTime: string, credentialScope: string, canonicalRequest: string): string
+  generateSignature(
+    params: {
+      method: 'GET' | 'POST'
+      host: string
+      path: string
+      query: Record<string, string>
+      headers: Record<string, string>
+      body?: string
+      service: string
+      region: string
+    },
+    credentials: { accessKeyId: string; secretAccessKey: string }
+  ): {
+    Authorization: string
+    'X-Date': string
+    'X-Content-Sha256': string
+    Host: string
+  }
+  loadCredentials(): Promise<{ accessKeyId: string; secretAccessKey: string } | null>
+  credentialsFilePath: string
+}
+
+const service = VolcengineService as VolcengineServiceType
+
+describe('VolcengineService', () => {
+  const mockEvent = {} as Electron.IpcMainInvokeEvent
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+    // Mock file system
+    vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+    vi.spyOn(fs.promises, 'writeFile').mockResolvedValue(undefined)
+    vi.spyOn(fs.promises, 'readFile').mockResolvedValue(Buffer.from(''))
+    vi.spyOn(fs.promises, 'unlink').mockResolvedValue(undefined)
+    vi.spyOn(fs.promises, 'mkdir').mockResolvedValue(undefined)
+    vi.spyOn(fs.promises, 'chmod').mockResolvedValue(undefined)
+  })
+
+  describe('Cryptographic Helper Methods', () => {
+    describe('sha256Hash', () => {
+      it('should correctly hash a string', () => {
+        const input = 'test string'
+        const expectedHash = crypto.createHash('sha256').update(input).digest('hex')
+
+        const result = service.sha256Hash(input)
+
+        expect(result).toBe(expectedHash)
+      })
+
+      it('should correctly hash a buffer', () => {
+        const input = Buffer.from('test buffer')
+        const expectedHash = crypto.createHash('sha256').update(input).digest('hex')
+
+        const result = service.sha256Hash(input)
+
+        expect(result).toBe(expectedHash)
+      })
+
+      it('should hash empty string', () => {
+        const expectedHash = crypto.createHash('sha256').update('').digest('hex')
+
+        const result = service.sha256Hash('')
+
+        expect(result).toBe(expectedHash)
+      })
+    })
+
+    describe('hmacSha256', () => {
+      it('should correctly compute HMAC-SHA256 with string key', () => {
+        const key = 'secret'
+        const data = 'message'
+        const expectedHmac = crypto.createHmac('sha256', key).update(data, 'utf8').digest()
+
+        const result = service.hmacSha256(key, data)
+
+        expect(result.equals(expectedHmac)).toBe(true)
+      })
+
+      it('should correctly compute HMAC-SHA256 with buffer key', () => {
+        const key = Buffer.from('secret')
+        const data = 'message'
+        const expectedHmac = crypto.createHmac('sha256', key).update(data, 'utf8').digest()
+
+        const result = service.hmacSha256(key, data)
+
+        expect(result.equals(expectedHmac)).toBe(true)
+      })
+    })
+
+    describe('hmacSha256Hex', () => {
+      it('should correctly compute HMAC-SHA256 and return hex string', () => {
+        const key = 'secret'
+        const data = 'message'
+        const expectedHex = crypto.createHmac('sha256', key).update(data, 'utf8').digest('hex')
+
+        const result = service.hmacSha256Hex(key, data)
+
+        expect(result).toBe(expectedHex)
+      })
+    })
+  })
+
+  describe('URL Encoding (RFC3986)', () => {
+    describe('uriEncode', () => {
+      it('should encode special characters', () => {
+        const input = 'hello world!@#$%^&*()'
+        const result = service.uriEncode(input)
+
+        // RFC3986 unreserved: A-Z a-z 0-9 - _ . ~
+        expect(result).toContain('hello%20world')
+        expect(result).toContain('%21') // !
+        expect(result).toContain('%40') // @
+      })
+
+      it('should not encode unreserved characters', () => {
+        const input = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~'
+        const result = service.uriEncode(input)
+
+        expect(result).toBe(input)
+      })
+
+      it('should encode slash by default', () => {
+        const input = 'path/to/resource'
+        const result = service.uriEncode(input)
+
+        expect(result).toBe('path%2Fto%2Fresource')
+      })
+
+      it('should not encode slash when encodeSlash is false', () => {
+        const input = 'path/to/resource'
+        const result = service.uriEncode(input, false)
+
+        expect(result).toBe('path/to/resource')
+      })
+
+      it('should handle empty string', () => {
+        const result = service.uriEncode('')
+
+        expect(result).toBe('')
+      })
+
+      it('should encode spaces as %20', () => {
+        const input = 'hello world'
+        const result = service.uriEncode(input)
+
+        expect(result).toBe('hello%20world')
+      })
+
+      it('should handle unicode characters', () => {
+        const input = '你好世界'
+        const result = service.uriEncode(input)
+
+        expect(result).not.toBe(input)
+        expect(result).toContain('%')
+      })
+    })
+  })
+
+  describe('Canonical Request Building', () => {
+    describe('buildCanonicalQueryString', () => {
+      it('should build sorted query string', () => {
+        const query = {
+          z: 'last',
+          a: 'first',
+          m: 'middle'
+        }
+
+        const result = service.buildCanonicalQueryString(query)
+
+        expect(result).toBe('a=first&m=middle&z=last')
+      })
+
+      it('should handle empty query object', () => {
+        const result = service.buildCanonicalQueryString({})
+
+        expect(result).toBe('')
+      })
+
+      it('should URL encode keys and values', () => {
+        const query = {
+          'key with space': 'value with space',
+          'special!@#': 'chars$%^'
+        }
+
+        const result = service.buildCanonicalQueryString(query)
+
+        expect(result).toContain('key%20with%20space=value%20with%20space')
+        expect(result).toContain('special%21%40%23=chars%24%25%5E')
+      })
+
+      it('should handle single parameter', () => {
+        const query = { action: 'ListModels' }
+
+        const result = service.buildCanonicalQueryString(query)
+
+        expect(result).toBe('action=ListModels')
+      })
+    })
+
+    describe('buildCanonicalHeaders', () => {
+      it('should lowercase and sort header names', () => {
+        // Headers should already be lowercase when passed to this method
+        const headers = {
+          'x-date': '20240101T120000Z',
+          'content-type': 'application/json',
+          host: 'example.com'
+        }
+
+        const result = service.buildCanonicalHeaders(headers)
+
+        expect(result.canonicalHeaders).toBe(
+          'content-type:application/json\nhost:example.com\nx-date:20240101T120000Z\n'
+        )
+        expect(result.signedHeaders).toBe('content-type;host;x-date')
+      })
+
+      it('should trim header values', () => {
+        // Headers should already be lowercase when passed to this method
+        const headers = {
+          host: '  example.com  ',
+          'x-date': '  20240101T120000Z  '
+        }
+
+        const result = service.buildCanonicalHeaders(headers)
+
+        expect(result.canonicalHeaders).toBe('host:example.com\nx-date:20240101T120000Z\n')
+      })
+
+      it('should handle empty header values', () => {
+        // Headers should already be lowercase when passed to this method
+        const headers = {
+          host: 'example.com',
+          'x-custom': ''
+        }
+
+        const result = service.buildCanonicalHeaders(headers)
+
+        expect(result.canonicalHeaders).toBe('host:example.com\nx-custom:\n')
+      })
+    })
+
+    describe('deriveSigningKey', () => {
+      it('should derive signing key correctly', () => {
+        const secretKey = 'testSecret'
+        const date = '20240101'
+        const region = 'cn-beijing'
+        const serviceName = 'ark'
+
+        const result = service.deriveSigningKey(secretKey, date, region, serviceName)
+
+        // The result should be a Buffer
+        expect(Buffer.isBuffer(result)).toBe(true)
+
+        // The key derivation should be deterministic
+        const result2 = service.deriveSigningKey(secretKey, date, region, serviceName)
+        expect(result.equals(result2)).toBe(true)
+      })
+
+      it('should produce different keys for different inputs', () => {
+        const secretKey = 'testSecret'
+        const date = '20240101'
+        const region = 'cn-beijing'
+        const serviceName = 'ark'
+
+        const key1 = service.deriveSigningKey(secretKey, date, region, serviceName)
+        const key2 = service.deriveSigningKey('differentSecret', date, region, serviceName)
+        const key3 = service.deriveSigningKey(secretKey, '20240102', region, serviceName)
+
+        expect(key1.equals(key2)).toBe(false)
+        expect(key1.equals(key3)).toBe(false)
+      })
+    })
+
+    describe('createCanonicalRequest', () => {
+      it('should create canonical request string correctly', () => {
+        const method = 'POST'
+        const canonicalUri = '/'
+        const canonicalQueryString = 'Action=ListModels&Version=2024-01-01'
+        const canonicalHeaders = 'host:open.volcengineapi.com\nx-date:20240101T120000Z\n'
+        const signedHeaders = 'host;x-date'
+        const payloadHash = 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+
+        const result = service.createCanonicalRequest(
+          method,
+          canonicalUri,
+          canonicalQueryString,
+          canonicalHeaders,
+          signedHeaders,
+          payloadHash
+        )
+
+        const expected = [
+          method,
+          canonicalUri,
+          canonicalQueryString,
+          canonicalHeaders,
+          signedHeaders,
+          payloadHash
+        ].join('\n')
+
+        expect(result).toBe(expected)
+      })
+    })
+
+    describe('createStringToSign', () => {
+      it('should create string to sign correctly', () => {
+        const dateTime = '20240101T120000Z'
+        const credentialScope = '20240101/cn-beijing/ark/request'
+        const canonicalRequest = 'POST\n/\n\nhost:example.com\n\nhost\npayloadhash'
+
+        const result = service.createStringToSign(dateTime, credentialScope, canonicalRequest)
+
+        const expectedHash = service.sha256Hash(canonicalRequest)
+        const expected = ['HMAC-SHA256', dateTime, credentialScope, expectedHash].join('\n')
+
+        expect(result).toBe(expected)
+      })
+    })
+  })
+
+  describe('Signature Generation', () => {
+    describe('generateSignature', () => {
+      it('should generate valid signature headers', () => {
+        const params = {
+          method: 'POST' as const,
+          host: 'open.volcengineapi.com',
+          path: '/',
+          query: { Action: 'ListModels', Version: '2024-01-01' },
+          headers: {},
+          body: '{}',
+          service: 'ark',
+          region: 'cn-beijing'
+        }
+
+        const credentials = {
+          accessKeyId: 'testAccessKey',
+          secretAccessKey: 'testSecretKey'
+        }
+
+        const result = service.generateSignature(params, credentials)
+
+        expect(result).toHaveProperty('Authorization')
+        expect(result).toHaveProperty('X-Date')
+        expect(result).toHaveProperty('X-Content-Sha256')
+        expect(result).toHaveProperty('Host')
+
+        // Verify Authorization header format
+        expect(result.Authorization).toContain('HMAC-SHA256')
+        expect(result.Authorization).toContain('Credential=testAccessKey')
+        expect(result.Authorization).toContain('SignedHeaders=')
+        expect(result.Authorization).toContain('Signature=')
+
+        // Verify Host header
+        expect(result.Host).toBe('open.volcengineapi.com')
+
+        // Verify X-Content-Sha256 matches body hash
+        const expectedBodyHash = service.sha256Hash('{}')
+        expect(result['X-Content-Sha256']).toBe(expectedBodyHash)
+
+        // Verify X-Date format (ISO8601 basic format)
+        expect(result['X-Date']).toMatch(/^\d{8}T\d{6}Z$/)
+      })
+
+      it('should handle empty body', () => {
+        const params = {
+          method: 'GET' as const,
+          host: 'open.volcengineapi.com',
+          path: '/',
+          query: {},
+          headers: {},
+          service: 'ark',
+          region: 'cn-beijing'
+        }
+
+        const credentials = {
+          accessKeyId: 'testAccessKey',
+          secretAccessKey: 'testSecretKey'
+        }
+
+        const result = service.generateSignature(params, credentials)
+
+        // Empty body should hash to specific value
+        const emptyHash = service.sha256Hash('')
+        expect(result['X-Content-Sha256']).toBe(emptyHash)
+      })
+
+      it('should generate consistent signatures for same input', () => {
+        const params = {
+          method: 'POST' as const,
+          host: 'open.volcengineapi.com',
+          path: '/',
+          query: { Action: 'ListModels' },
+          headers: {},
+          body: '{"test":true}',
+          service: 'ark',
+          region: 'cn-beijing'
+        }
+
+        const credentials = {
+          accessKeyId: 'testAccessKey',
+          secretAccessKey: 'testSecretKey'
+        }
+
+        try {
+          // Mock Date to ensure consistent timestamp
+          const mockDate = new Date('2024-01-01T12:00:00Z')
+          vi.useFakeTimers()
+          vi.setSystemTime(mockDate)
+
+          const result1 = service.generateSignature(params, credentials)
+          const result2 = service.generateSignature(params, credentials)
+
+          expect(result1.Authorization).toBe(result2.Authorization)
+          expect(result1['X-Date']).toBe(result2['X-Date'])
+          expect(result1['X-Content-Sha256']).toBe(result2['X-Content-Sha256'])
+        } finally {
+          vi.useRealTimers()
+        }
+      })
+    })
+  })
+
+  describe('Credential Management', () => {
+    describe('saveCredentials', () => {
+      it('should save credentials using safeStorage', async () => {
+        vi.mocked(safeStorage.isEncryptionAvailable).mockReturnValue(true)
+
+        await service.saveCredentials(mockEvent, 'testAccessKey', 'testSecretKey')
+
+        expect(safeStorage.encryptString).toHaveBeenCalledWith(
+          JSON.stringify({
+            accessKeyId: 'testAccessKey',
+            secretAccessKey: 'testSecretKey'
+          })
+        )
+        expect(fs.promises.writeFile).toHaveBeenCalled()
+        expect(fs.promises.chmod).toHaveBeenCalledWith(expect.any(String), 0o600)
+      })
+
+      it('should throw error when credentials are empty', async () => {
+        await expect(service.saveCredentials(mockEvent, '', 'secret')).rejects.toThrow(
+          'Access Key ID and Secret Access Key are required'
+        )
+
+        await expect(service.saveCredentials(mockEvent, 'key', '')).rejects.toThrow(
+          'Access Key ID and Secret Access Key are required'
+        )
+      })
+
+      it('should throw error when safeStorage is not available', async () => {
+        vi.mocked(safeStorage.isEncryptionAvailable).mockReturnValue(false)
+
+        await expect(service.saveCredentials(mockEvent, 'key', 'secret')).rejects.toThrow(
+          'Secure storage is not available on this platform'
+        )
+      })
+
+      it('should create directory if it does not exist', async () => {
+        vi.mocked(safeStorage.isEncryptionAvailable).mockReturnValue(true)
+        vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+
+        await service.saveCredentials(mockEvent, 'testAccessKey', 'testSecretKey')
+
+        expect(fs.promises.mkdir).toHaveBeenCalledWith(expect.any(String), { recursive: true })
+      })
+    })
+
+    describe('loadCredentials', () => {
+      it('should return null when credentials file does not exist', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+
+        const result = await service.loadCredentials()
+
+        expect(result).toBeNull()
+      })
+
+      it('should load and decrypt credentials when file exists', async () => {
+        const mockCredentials = {
+          accessKeyId: 'testAccessKey',
+          secretAccessKey: 'testSecretKey'
+        }
+
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(`encrypted:${JSON.stringify(mockCredentials)}`)
+        )
+
+        const result = await service.loadCredentials()
+
+        expect(result).toEqual(mockCredentials)
+        expect(safeStorage.decryptString).toHaveBeenCalled()
+      })
+
+      it('should throw error for corrupted credentials file', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(Buffer.from('corrupted-data'))
+        vi.mocked(safeStorage.decryptString).mockImplementation(() => {
+          throw new Error('Decryption failed')
+        })
+
+        await expect(service.loadCredentials()).rejects.toThrow(
+          'Credentials file exists but could not be loaded'
+        )
+      })
+
+      it('should throw error for invalid JSON in credentials', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(Buffer.from('encrypted:invalid-json'))
+
+        await expect(service.loadCredentials()).rejects.toThrow(
+          'Credentials file exists but could not be loaded'
+        )
+      })
+    })
+
+    describe('hasCredentials', () => {
+      it('should return true when credentials file exists', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+
+        const result = await service.hasCredentials()
+
+        expect(result).toBe(true)
+      })
+
+      it('should return false when credentials file does not exist', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+
+        const result = await service.hasCredentials()
+
+        expect(result).toBe(false)
+      })
+    })
+
+    describe('clearCredentials', () => {
+      it('should delete credentials file when it exists', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+
+        await service.clearCredentials()
+
+        expect(fs.promises.unlink).toHaveBeenCalled()
+      })
+
+      it('should not throw error when credentials file does not exist', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+
+        await expect(service.clearCredentials()).resolves.not.toThrow()
+        expect(fs.promises.unlink).not.toHaveBeenCalled()
+      })
+
+      it('should throw error when file deletion fails', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.unlink).mockRejectedValue(new Error('Permission denied'))
+
+        await expect(service.clearCredentials()).rejects.toThrow('Failed to clear credentials')
+      })
+    })
+  })
+
+  describe('API Methods', () => {
+    describe('listModels', () => {
+      it('should fetch and combine foundation models and endpoints', async () => {
+        const mockFoundationModelsResponse = {
+          Result: {
+            TotalCount: 2,
+            Items: [
+              { Name: 'model1', DisplayName: 'Model 1', Description: 'Test model 1' },
+              { Name: 'model2', DisplayName: 'Model 2', Description: 'Test model 2' }
+            ]
+          }
+        }
+
+        const mockEndpointsResponse = {
+          Result: {
+            TotalCount: 1,
+            Items: [
+              {
+                Id: 'ep-123',
+                Name: 'Custom Endpoint',
+                Description: 'Custom endpoint',
+                ModelReference: {
+                  FoundationModel: {
+                    Name: 'base-model',
+                    ModelVersion: 'v1.0'
+                  }
+                }
+              }
+            ]
+          }
+        }
+
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        // Mock API calls
+        vi.mocked(net.fetch)
+          .mockResolvedValueOnce({
+            ok: true,
+            json: async () => mockFoundationModelsResponse
+          } as any)
+          .mockResolvedValueOnce({
+            ok: true,
+            json: async () => mockEndpointsResponse
+          } as any)
+
+        const result = await service.listModels(mockEvent)
+
+        expect(result.models).toHaveLength(3)
+        expect(result.total).toBe(3)
+        expect(result.models[0].id).toBe('model1')
+        expect(result.models[2].id).toBe('ep-123')
+      })
+
+      it('should handle partial failures gracefully', async () => {
+        const mockFoundationModelsResponse = {
+          Result: {
+            TotalCount: 1,
+            Items: [{ Name: 'model1', DisplayName: 'Model 1' }]
+          }
+        }
+
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        // Mock API calls - first succeeds, second fails
+        vi.mocked(net.fetch)
+          .mockResolvedValueOnce({
+            ok: true,
+            json: async () => mockFoundationModelsResponse
+          } as any)
+          .mockResolvedValueOnce({
+            ok: false,
+            status: 500,
+            text: async () => 'Server error'
+          } as any)
+
+        const result = await service.listModels(mockEvent)
+
+        expect(result.models).toHaveLength(1)
+        expect(result.warnings).toBeDefined()
+        expect(result.warnings?.length).toBeGreaterThan(0)
+      })
+
+      it('should throw error when both API calls fail', async () => {
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        // Mock both API calls to fail
+        vi.mocked(net.fetch).mockResolvedValue({
+          ok: false,
+          status: 500,
+          text: async () => 'Server error'
+        } as any)
+
+        await expect(service.listModels(mockEvent)).rejects.toThrow(
+          'Failed to fetch both foundation models and endpoints'
+        )
+      })
+
+      it('should throw error when no credentials are found', async () => {
+        vi.spyOn(fs, 'existsSync').mockReturnValue(false)
+
+        await expect(service.listModels(mockEvent)).rejects.toThrow(
+          'No credentials found. Please save credentials first.'
+        )
+      })
+    })
+
+    describe('getAuthHeaders', () => {
+      it('should generate auth headers for external use', async () => {
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        const params = {
+          method: 'POST' as const,
+          host: 'open.volcengineapi.com',
+          path: '/v1/chat/completions',
+          query: {},
+          body: '{"model":"test"}'
+        }
+
+        const result = await service.getAuthHeaders(mockEvent, params)
+
+        expect(result).toHaveProperty('Authorization')
+        expect(result).toHaveProperty('X-Date')
+        expect(result).toHaveProperty('X-Content-Sha256')
+        expect(result).toHaveProperty('Host')
+      })
+
+      it('should use default service and region when not provided', async () => {
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        const params = {
+          method: 'POST' as const,
+          host: 'open.volcengineapi.com',
+          path: '/',
+          query: {}
+        }
+
+        const result = await service.getAuthHeaders(mockEvent, params)
+
+        // Should not throw and should generate headers
+        expect(result).toHaveProperty('Authorization')
+        expect(result.Authorization).toContain('cn-beijing/ark/request')
+      })
+    })
+
+    describe('makeRequest', () => {
+      it('should make a generic signed API request', async () => {
+        const mockResponse = { success: true, data: 'test' }
+
+        // Setup credentials
+        vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+        vi.mocked(fs.promises.readFile).mockResolvedValue(
+          Buffer.from(
+            `encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`
+          )
+        )
+
+        vi.mocked(net.fetch).mockResolvedValue({
+          ok: true,
+          json: async () => mockResponse
+        } as any)
+
+        const params = {
+          method: 'POST' as const,
+          host: 'open.volcengineapi.com',
+          path: '/',
+          action: 'TestAction',
+          version: '2024-01-01',
+          query: {},
+          body: { test: true }
+        }
+
+        const result = await service.makeRequest(mockEvent, params)
+
+        expect(result).toEqual(mockResponse)
+        expect(net.fetch).toHaveBeenCalled()
+      })
+    })
+  })
+
+  describe('Error Handling', () => {
+    it('should handle network errors in API requests', async () => {
+      // Setup credentials
+      vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+      vi.mocked(fs.promises.readFile).mockResolvedValue(
+        Buffer.from(`encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`)
+      )
+
+      vi.mocked(net.fetch).mockRejectedValue(new Error('Network error'))
+
+      await expect(service.listModels(mockEvent)).rejects.toThrow('Failed to list models')
+    })
+
+    it('should handle API error responses', async () => {
+      // Setup credentials
+      vi.spyOn(fs, 'existsSync').mockReturnValue(true)
+      vi.mocked(fs.promises.readFile).mockResolvedValue(
+        Buffer.from(`encrypted:${JSON.stringify({ accessKeyId: 'test', secretAccessKey: 'test' })}`)
+      )
+
+      vi.mocked(net.fetch).mockResolvedValue({
+        ok: false,
+        status: 401,
+        text: async () => 'Unauthorized'
+      } as any)
+
+      await expect(service.listModels(mockEvent)).rejects.toThrow()
+    })
+  })
+})