stubfetch

Deterministic, in-process fake HTTP APIs for testing agents and tools. Swap real network calls for canned GitHub, Stripe, Postgres-shaped data, OpenAI / Anthropic-style LLM JSON, S3-like objects, Slack Web API responses—while recording traffic, exporting JSON / Markdown / HAR, running eval scenarios, and optionally injecting chaos (latency, random failures).

Same ideas in TypeScript (npm) and Python (PyPI / local install).

Install

JavaScript / TypeScript (npm)

npm install stubfetch

Requires Node.js ≥ 18. No runtime npm dependencies.

Python

pip install stubfetch

From a clone (editable):

pip install -e ./python

Requires Python ≥ 3.10.

Quick start

TypeScript

import { GhostEnv, github, exportRecordingJSON } from "stubfetch";

const env = new GhostEnv({
  seed: 42,
  providers: [github({ issues: [{ repo: "acme/api", title: "Bug" }] })],
});

const res = await env.fetch("https://api.github.com/repos/acme/api/issues");
console.log(await res.json());
console.log(exportRecordingJSON(env.calls()));

Python

from stubfetch import GhostEnv, github, export_recording_json

env = GhostEnv(
    {"seed": 1, "providers": [github({"issues": [{"repo": "acme/api", "title": "Bug"}]})]}
)
status, text = env.fetch("https://api.github.com/repos/acme/api/issues")
assert status == 200
print(export_recording_json(env.calls()))

Features

Documentation

Hosted on slaps.dev:

License

Apache-2.0