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Web Standards
- Web Standards Reference
- Encoding Reference
- Fetch Reference
- Request Reference
- Response Reference
- Streams Reference
- Web Crypto Reference
Mocking Outbound fetch Requests
When using the API, Miniflare allows you to substitute custom Responses for
fetch() calls using undici's
MockAgent API ↗.
This is useful for testing Workers that make HTTP requests to other services. To
enable fetch mocking, create a
MockAgent ↗
using the createFetchMock() function, then set this using the fetchMock
option.
import { Miniflare, createFetchMock } from "miniflare";
// Create `MockAgent` and connect it to the `Miniflare` instance
const fetchMock = createFetchMock();
const mf = new Miniflare({
modules: true,
script: `
export default {
async fetch(request, env, ctx) {
const res = await fetch("https://example.com/thing");
const text = await res.text();
return new Response(\`response:\${text}\`);
}
}
`,
fetchMock,
});
// Throw when no matching mocked request is found
// (see https://undici.nodejs.org/#/docs/api/MockAgent?id=mockagentdisablenetconnect)
fetchMock.disableNetConnect();
// Mock request to https://example.com/thing
// (see https://undici.nodejs.org/#/docs/api/MockAgent?id=mockagentgetorigin)
const origin = fetchMock.get("https://example.com");
// (see https://undici.nodejs.org/#/docs/api/MockPool?id=mockpoolinterceptoptions)
origin
.intercept({ method: "GET", path: "/thing" })
.reply(200, "Mocked response!");
const res = await mf.dispatchFetch("http://localhost:8787/");
console.log(await res.text()); // "response:Mocked response!"Subrequests
Miniflare does not support limiting the amount of subrequests. Please keep this in mind if you make a large amount of subrequests from your Worker.
