@dever-labs/mockly-driver

@dever-labs/mockly-driver

Node.js client for Mockly — start, stop, and control Mockly HTTP mock servers from Node.js test suites.

import { MocklyServer } from '@dever-labs/mockly-driver'

const server = await MocklyServer.ensure() // download binary if needed, then start

await server.addMock({
  id: 'get-users',
  request: { method: 'GET', path: '/users' },
  response: { status: 200, body: '[{"id":1}]', headers: { 'Content-Type': 'application/json' } },
})

const res = await fetch(`${server.httpBase}/users`)
// → 200 [{"id":1}]

await server.stop()

Installation

npm install --save-dev @dever-labs/mockly-driver

The Mockly binary is downloaded automatically for your platform when you run npm install. You can also trigger it manually:

npx mockly-install

---

Usage

MocklyServer.ensure(opts?) (recommended)

Downloads the binary if missing, then starts the server.

const server = await MocklyServer.ensure()

MocklyServer.create(opts?)

Starts the server using an already-installed binary. Throws if the binary is not found.

const server = await MocklyServer.create()

Test framework integration

// vitest / jest
import { MocklyServer } from '@dever-labs/mockly-driver'

let server: MocklyServer

beforeAll(async () => {
  server = await MocklyServer.ensure()
}, 30_000)

afterAll(() => server?.stop())

beforeEach(() => server.reset()) // isolate each test

it('returns 200', async () => {
  await server.addMock({
    id: 'ping',
    request: { method: 'GET', path: '/ping' },
    response: { status: 200, body: 'pong' },
  })
  const res = await fetch(`${server.httpBase}/ping`)
  expect(res.status).toBe(200)
})

---

Management API

server.addMock(mock)

Adds an HTTP mock. Mocks are matched in insertion order — first match wins.

await server.addMock({
  id: 'create-user',
  request: {
    method: 'POST',
    path: '/users',
    headers: { Authorization: 'Bearer mytoken' }, // exact match
  },
  response: {
    status: 201,
    body: '{"id":42}',
    headers: { 'Content-Type': 'application/json' },
    delay: '50ms',
  },
})

Note: Header matching is exact. Place mocks with header constraints before less-specific fallbacks.

server.deleteMock(id)

Removes a mock by id.

server.reset()

Removes all dynamically added mocks, deactivates scenarios, and clears fault injection. Mocks defined in startup config are preserved. Call in beforeEach to keep tests isolated.

Scenarios

Scenarios override mock responses when activated — useful for simulating outage modes.

const server = await MocklyServer.ensure({
  scenarios: [
    {
      id: 'auth-down',
      name: 'Auth service unavailable',
      patches: [{ mock_id: 'token-endpoint', status: 503, body: '{"error":"down"}' }],
    },
  ],
})

await server.addMock({
  id: 'token-endpoint',
  request: { method: 'POST', path: '/token' },
  response: { status: 200, body: '{"access_token":"abc"}' },
})

// Normal operation
const r1 = await fetch(`${server.httpBase}/token`, { method: 'POST' })
// → 200

await server.activateScenario('auth-down')

const r2 = await fetch(`${server.httpBase}/token`, { method: 'POST' })
// → 503

await server.deactivateScenario('auth-down')

Fault injection

// Delay every response by 200 ms
await server.setFault({ enabled: true, delay: '200ms' })

// Override all responses with 503
await server.setFault({ enabled: true, status: 503 })

// Randomly fail 30% of requests
await server.setFault({ enabled: true, status: 503, error_rate: 0.3 })

await server.clearFault()

---

Binary installation

The binary is downloaded automatically on npm install via a postinstall script. The version downloaded always matches the npm package version.

Manual install

npx mockly-install

Or programmatically:

import { install } from '@dever-labs/mockly-driver'
await install()

Artifactory / internal mirror

Set MOCKLY_DOWNLOAD_BASE_URL to your mirror's base URL (the path up to and including the version segment prefix):

MOCKLY_DOWNLOAD_BASE_URL=https://artifactory.company.com/artifactory/github-releases/dever-labs/mockly/releases/download \
  npx mockly-install

Artifactory setup: create a Generic Remote Repository pointing to https://github.com and enable "Store Artifacts Locally". The download URL then becomes https://<artifactory>/artifactory/<repo>/dever-labs/mockly/releases/download.

HTTP / HTTPS proxy

Set HTTPS_PROXY or HTTP_PROXY before running the install:

HTTPS_PROXY=https://proxy.company.com:3128 npx mockly-install

Proxy authentication is supported via the proxy URL: https://user:pass@proxy:3128.

Note: If your proxy username or password contains special characters (e.g. @, :, /), URL-encode them first — e.g. p@ss → p%40ss.

Tip: For Artifactory, MOCKLY_DOWNLOAD_BASE_URL is simpler and more reliable than HTTPS_PROXY.

Air-gapped environments

Pre-stage the binary and point to it:

# On a machine with internet access:
npx mockly-install

# Copy bin/mockly[.exe] to the air-gapped machine, then:
MOCKLY_BINARY_PATH=/opt/tools/mockly npx vitest run

Or set MOCKLY_NO_INSTALL=true to make a missing binary a hard error:

MOCKLY_NO_INSTALL=true npx vitest run  # fails fast if binary not staged

Environment variable reference

Variable	Description
MOCKLY_BINARY_PATH	Absolute path to a pre-existing binary. Skips all download logic.
MOCKLY_DOWNLOAD_BASE_URL	Base URL override for binary downloads (Artifactory / mirrors).
MOCKLY_VERSION	Binary version to install. Defaults to the installed package version.
MOCKLY_NO_INSTALL	If set, fail with instructions instead of downloading.
HTTPS_PROXY / HTTP_PROXY	Route downloads through an HTTP proxy (supports CONNECT).

---

Requirements

• Node.js ≥ 18
• Platforms: Linux (x64/arm64), macOS (x64/arm64), Windows (x64)

License

MIT