Does Keploy replace deno test + fetch stubs?

No. Keep deno test + fetch stubs 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 Deno 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.

Do I need extra Deno permissions to record?

Recording uses whatever permissions your service already runs with. Replay needs fewer, not more: the dependencies come from the recording, so no --allow-net is required for them.

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 Deno testing framework

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

Generate Deno tests free

keploy record -c "deno run --allow-all main.ts"

18.4K+

1.2M+300M+mocks createdSlack

What Keploy gives a Deno team

Any Deno service, unchanged

Keploy runs the process you already run with deno run. Oak, Hono, Fresh and a bare Deno.serve handler all record identically, because capture is at the socket rather than inside the runtime.

Deno 1.x and 2.x
Oak, Hono, Fresh, Deno.serve
npm: and jsr: specifiers alike
No import map changes

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The problem

Why Deno 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 Deno: by hand, with deno test + fetch stubs, or with Keploy

deno test + fetch stubs describes the exchange by hand and still needs the dependency supplied. Keploy records both halves once and replays them with nothing running.

By hand

deno test + fetch stubs

With Keploy

Select any row for the full comparison, with code.

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Same coverage, three costs

What you write for Deno 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.ts

hand-written

import { assertEquals } from "jsr:@std/assert";

import { handler } from "./orders.ts";

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

const db = {

queryObject: () =>

Promise.resolve({ rows: [{ id: "o-1", total: 4200, status: "NEW" }] }),

};

const realFetch = globalThis.fetch;

Deno.test("confirms an order", async () => {

// Replace the runtime's own fetch, and remember to put it back.

globalThis.fetch = () =>

Promise.resolve(new Response(JSON.stringify({ status: "AUTHORIZED" })));

try {

const res = await handler(new Request("http://localhost/orders/o-1/confirm", {

method: "POST",

}), db);

assertEquals(res.status, 200);

} finally {

globalThis.fetch = realFetch;

}

});

The stub and the fake client exist only for this test.

deno test + fetch stubs1–2 hours

orders_stub_test.ts

tool-assisted

import { assertEquals } from "jsr:@std/assert";

import { Client } from "jsr:@db/postgres";

import { handler } from "./orders.ts";

// A real Postgres, so the job needs one running.

const db = new Client(Deno.env.get("DATABASE_URL"));

await db.connect();

// A stub upstream on a real port, which the handler must be pointed at.

const stub = Deno.serve({ port: 8787 }, () =>

new Response(JSON.stringify({ status: "AUTHORIZED" })),

);

Deno.test("confirms an order", async () => {

Deno.env.set("PAYMENTS_URL", "http://localhost:8787");

const res = await handler(new Request("http://localhost/orders/o-1/confirm", {

method: "POST",

}), db);

assertEquals(res.status, 200);

});

A stub server per upstream, and a real database to seed.

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

Deno 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 Deno app once, replay it forever

Keploy sits below your Deno 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 Deno appGET/api/v1/orders/{id}200

RecordingKeploy proxyeBPF · userspace

PostgreSQLPostgres protocol beneath deno-postgres

MySQLMySQL protocol beneath the Deno driver

RedisRESP beneath the Deno Redis client

MongoDBWire protocol beneath the Deno Mongo driver

+2 more Deno 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 Deno, with zero config

5 of the 6 dependencies a typical Deno 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 deno-postgres
Auto-mocked
MySQLView page
MySQL protocol beneath the Deno driver
Auto-mocked
RedisView page
RESP beneath the Deno Redis client
Auto-mocked
MongoDBView page
Wire protocol beneath the Deno Mongo driver
Outbound HTTP
Auto-mocked
Outbound HTTP
Every globalThis.fetch call
Partial
gRPCView page
HTTP/2 frames from a Deno gRPC client

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Quick start

Your first Deno test suite in under five minutes

Every command below runs against your existing Deno 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 "deno run --allow-all main.ts"
3
3Exercise the paths you care about
Use curl, your frontend, or an existing smoke script. Every request becomes a test case with its Deno calls captured alongside it.
curl -X POST localhost:8000/orders/o-1/confirm
curl localhost:8000/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 "deno run --allow-all main.ts" --delay 10