Fetch.functions.makeMockLayer

fx-fetch

---

fx-fetch / Fetch / makeMockLayer

Function: makeMockLayer()

makeMockLayer(mockFn): Layer<Fetch, never, never>

Defined in: packages/fx-fetch/src/Fetch/makeMockLayer.ts:55

Creates a mock Fetch layer for testing purposes.

The mock function can return either a plain Response or an Effect<Response, E> for simulating both successful responses and error scenarios.

Parameters

mockFn

MockFn

Returns

Layer<Fetch, never, never>

Examples

import { Effect } from 'effect';
import { Fetch, Request, Response } from 'fx-fetch';

// Mock returning a simple Response
const mockLayer = Fetch.makeMockLayer(() =>
  Response.unsafeMake({ status: 200, ok: true, body: 'Hello' })
);

Effect.gen(function* () {
  const request = Request.unsafeMake({ url: 'https://example.com' });
  const response = yield* Fetch.fetch(request);
}).pipe(
  Effect.provide(mockLayer), // ◀︎── Provide mock layer
  Effect.runPromise
);

import { Effect } from 'effect';
import { Fetch, Request, Response, Url } from 'fx-fetch';

// Mock using the request to return different responses
const mockLayer = Fetch.makeMockLayer((request) => {
  if (Url.format(request.url).includes('/users')) {
    return Response.unsafeMake({ status: 200, ok: true, body: JSON.stringify([{ id: 1 }]) });
  }

  return Response.unsafeMake({ status: 404, ok: false });
});

Since

1.2.0