Does Keploy replace Jest + Sinon?

No. Keep Jest + Sinon for unit tests, where it is the right tool. Keploy covers the integration layer, where the cost is the dependencies rather than the assertions.

Do I have to change my JavaScript code?

No. Keploy runs the process you already run and captures at the socket, so no annotation, no wrapper and no dependency injection change is needed.

What happens when a dependency changes?

Re-record. One command refreshes every captured interaction in the suite, so a changed contract shows up as a diff rather than as a silently passing stale mock.

Does it work with ESM and CommonJS?

Yes. Module format is irrelevant, because nothing is captured at the module boundary. A query or an HTTP call is captured at the protocol beneath it.

Can I run this in CI?

Yes, and that is the point: replay needs nothing running. No database service, no broker, no network access to upstreams, so the job is the same on every runner.

Keploy as a JavaScript testing framework

Keploy tests JavaScript services by recording real HTTP and database traffic from a running process, then replaying it as assertions. There is no module registry to patch and nothing to mock by hand, because capture happens below the runtime at the socket.

Generate JavaScript tests free

keploy record -c "node server.js"

18.4K+

1.2M+300M+mocks createdSlack

What Keploy gives a JavaScript team

Any JavaScript service, unchanged

Keploy runs the process you already run with node. Express, Fastify, Koa, Hapi and a bare http server all record identically, because capture is at the socket rather than inside the framework.

Node 14 and above
Express, Fastify, Koa, Hapi
CommonJS and ESM alike
No bundler changes

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The problem

Why JavaScript integration tests slow teams down

The friction is rarely the assertions. It is everything around them — spinning up dependencies, keeping mocks honest, and repairing tests after every refactor.

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Three ways to do it

Testing JavaScript: by hand, with Jest + Sinon, or with Keploy

Jest + Sinon describes the exchange by hand and still needs the dependency supplied. Keploy records both halves once and replays them with nothing running.

By hand

Jest + Sinon

With Keploy

Select any row for the full comparison, with code.

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Same coverage, three costs

What you write for JavaScript vs what Keploy records

All three produce the same assertion. Only the third still passes after the next refactor without anyone editing it.

By hand2–4 hours

orders.test.js

hand-written

const request = require('supertest');

const { app } = require('./app');

// A fake Postgres client, so the driver never runs.

jest.mock('./db', () => ({

findOrder: () => Promise.resolve({ id: 'o-1', total: 4200, status: 'NEW' }),

}));

// And the upstream, stubbed per URL.

jest.mock('node-fetch', () => () =>

Promise.resolve({ json: () => ({ status: 'AUTHORIZED' }) }),

);

test('confirms an order', async () => {

const res = await request(app).post('/orders/o-1/confirm');

expect(res.status).toBe(200);

expect(res.body.status).toBe('CONFIRMED');

});

The fakes exist only for this test and drift the moment the schema does.

Jest + Sinon1–2 hours

orders.nock.test.js

tool-assisted

const request = require('supertest');

const nock = require('nock');

const { app } = require('./app');

beforeEach(() => {

// One interceptor per outbound URL, written by hand.

nock('https://api.payments.example.com')

.post('/v1/payment_intents/tok_123/confirm')

.reply(200, { status: 'AUTHORIZED' });

});

// A real Postgres is still needed, seeded before the run.

test('confirms an order', async () => {

const res = await request(app).post('/orders/o-1/confirm');

expect(res.status).toBe(200);

});

Jest + Sinon handles the HTTP half. The database is still yours to run.

With Keploy~5 minutes

keploy/test-set-0/test-1.yaml

auto-generated

version: api.keploy.io/v1beta1

kind: Http

name: test-1

spec:

req:

method: POST

url: /orders/o-1/confirm

resp:

status_code: 200

body: '{"id":"o-1","status":"CONFIRMED","total":4200}'

assertions:

noise:

- body.confirmedAt

---

kind: Postgres

spec:

query: select id, total, status from orders where id = $1

rows:

- { id: "o-1", total: 4200, status: "NEW" }

---

kind: Http

spec:

request:

url: https://api.payments.example.com/v1/payment_intents/tok_123/confirm

response:

body: '{"status":"AUTHORIZED"}'

Recorded from one real request. Nothing here was typed by hand.

Times are estimates for authoring one endpoint’s coverage from scratch, not measurements.

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Keploy vs the alternatives

JavaScript testing tools, compared

The options a team on Node.js actually reaches for, and where each one genuinely wins. Select a row for the full comparison.

Keploy

Jest + supertest

nock

Mocha + Sinon

Mock Service Worker

Postman

SmartBear ReadyAPI

Best in classStrongPartialNot covered

Assessments reflect each tool’s documented behaviour, not benchmark measurements.

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How it works

Record your JavaScript app once, replay it forever

Keploy sits below your JavaScript process at the network layer. It watches the calls your app already makes, then serves them back on replay so tests run with no dependencies attached.

Your JavaScript appGET/api/v1/orders/{id}200

RecordingKeploy proxyeBPF · userspace

PostgreSQLPostgres protocol beneath pg and Knex

MySQLMySQL protocol beneath mysql2

MongoDBWire protocol beneath the Mongo driver

RedisRESP beneath ioredis and node-redis

+3 more JavaScript dependencies

An example shape of a captured call. Your own endpoints and dependencies come from your real traffic, so nothing here has to be written by hand.

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Mock coverage

What Keploy mocks for JavaScript, with zero config

6 of the 7 dependencies a typical JavaScript service talks to are stubbed from the recording itself — no mock classes, no fixture files, no containers in CI.

Auto-mocked
PostgreSQLView page
Postgres protocol beneath pg and Knex
Auto-mocked
MySQLView page
MySQL protocol beneath mysql2
Auto-mocked
MongoDBView page
Wire protocol beneath the Mongo driver
Auto-mocked
RedisView page
RESP beneath ioredis and node-redis
Outbound HTTP
Auto-mocked
Outbound HTTP
Every fetch, axios and got call
Auto-mocked
Apache KafkaView page
Kafka protocol beneath kafkajs
Partial
gRPCView page
HTTP/2 frames from a Node gRPC client

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Quick start

Your first JavaScript test suite in under five minutes

Every command below runs against your existing JavaScript service. Nothing in your source tree changes.

1
1Install the Keploy CLI
A single binary. It needs a Linux kernel with eBPF support, or Docker on macOS and Windows — and it adds nothing to your project's dependencies.
curl -sSL https://keploy.io/install.sh | bash
2
2Record your service
Pass the command you already use to start the app. Keploy runs it and watches every socket it opens.
keploy record -c "node server.js"
3
3Exercise the paths you care about
Use curl, your frontend, or an existing smoke script. Every request becomes a test case with its JavaScript calls captured alongside it.
curl -X POST localhost:3000/orders/o-1/confirm
curl localhost:3000/orders/o-1
4
4Replay in CI
Replay serves the recorded dependency responses, so the job needs no service containers and no Docker daemon.
keploy test -c "node server.js" --delay 10