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A small, simple http server for mocking and asserting http calls.


npm install simple-fake-server --save-dev
yarn add simple-fake-server

Usage Example

import { FakeServer } from 'simple-fake-server');

describe('Test Example', () => {
    let fakeServer;

    before(() => {
        fakeServer = new FakeServer(1234);
        fakeServer.start(); //The FakeServer now listens on http://localhost:1234

    it('Does something', async () => {
        const route = fakeServer.get('/your/api').willReturn({ message: "hello world" });

        const response = await fetch('http://localhost:1234/your/api', { method: 'GET' });
        const body = await response.json();

        expect(body.message).toEqual("hello world");

    after(() => {
        fakeServer.stop(); // stop listening

Running Inside a Docker Container

see simple-fake-server-server

Defining Routes

const route = fakeServer
    .get(pathRegex) // Http Method and route (route may be a regex). See Supported HTTP Methods section.
    .withBody(object) // Route Restriction (optional). The server will only respond to requests matching the restriction. See Route Restrictions section for more info.
    .willSucceed(); // Route Response (mandatory). See Response Section for more info.

Supported HTTP Methods

The following http methods are supported:

  • get
  • post
  • put
  • delete
  • patch


Response is mandatory and needs to be set on any defined route.

  • willSucceed() - a request to a route that was defined with willSucceed will return 200 as the status code and {} as the response body.

  • willFail(errorStatusCode?: number) - a request to route that was defined with willFail will return errorStatusCode as the status code (or default to 500 if none provided) and {} as the response body.

  • willReturn(response: any, statusCode?: number) - a request to route that was defined with willReturn will return status code statusCode (default is 200 if none provided) and response as the response body.

Route Restrictions

Restrictions are optional and can be defined after calling FakeHttpServer.{method}(path). Only one restriction can be set per route definition.
Chaining more than one restriction will result in an error.

  • withBody(body: object)
    Will match only requests with content-type header set to 'application/json' and body that is an objects that deeply equal the given body:
const withBodyRoute ='/some/path').withBody({a: 1, b: 2}).willSucceed();

// Request to /some/path with body { a: 1, b: 2 } => Success, 200 status code.
// Request to /some/path with body { a: 1, b: 2, c: 3 } => Fail, 400 status code.
  • withBodyThatMatches(regex: string)
    Will match only requests with body that match the given regex.
    i.e. route defined with withBodyThatMatches('[a-zA-Z]+$') will accept request body abc but will reject 123.

  • withBodyThatContains(partialObject: object)
    Will match only requests with content-type header set to 'application/json' and body that is a superset of the given body. i.e. route defined with withBodyThatContains({ a: 1, b: 2 }) will accept request body { a: 1, b: 2, c: 3} but will reject a request with { a: 1 } as the body.

  • withQueryParams(queryParams: object)
    Will only match requests that match the query params set on queryParams.

    i.e. route defined with withQueryParams({ someQuery: true }) will match requests to some/path?someQuery=true but will reject some/path?someQuery=false or some/path?someQuery=true&other=something.


  • A request that failed to fulfill a restriction will return 400 and will result in false when asserting with didReceive (more on this on the next section).

  • When setting 2 or more routes with the same path, but with different body restrictions, it's enough to fulfill just 1 of the restrictions to get a match.


Each route exposes a RouteCallTester object that can be accessed using

const route = fakeServer.get('/some/path').willSucceed();

const routeCallTester =;

Assertion Methods

FakeServer instance exposes 3 methods that can be helpful for your tests assertions.

  • didReceive(routeCallTester: RouteCallTester)
    Returns true/false, based on whether this route was called since the server was started.
    Usage example:
const route = fakeServer.get('/your/api').willSucceed();

console.log(fakeServer.hasMade(; // false
await fetch('http://localhost:1234/your/api', {method: 'GET'});
console.log(fakeServer.hasMade(; // true
  • callsReceived(routeCallTester: RouteCallTester)
    Returns an array of all calls received that match the provided route.
    Each entry of the array is an object containing method, path, headers and body.

  • clearCallHistory()
    After calling clearCallHistory hasMade will always return false and callsMade will always return an empty array until the next call is made.

Assertion Constrains

It's possible to add a constrain to the routeCallTester. It's useful when the route was defined with a regex or a body restriction and you want to make sure exactly what was the route called with.

  • withPath(specificPath: string)
    Useful when defining a route with regex and you'd like to assert a specific path was called.
    Usage example:
await fetch('/some/path/xyz', {method: 'GET'});

console.log(fakeServer.didReceive('/some/path/xyz'))); // true
console.log(fakeServer.didReceive('/some/path/abc'))); // false
  • withBodyText(text: string)

    Useful when defining a route with withBodyThatMatches using regex and you'd like to assert a specific body text.

  • withSpecificBody(body: object)
    Useful when defining a route with withBodyThatContains and you'd like to assert a specific body object.

More Usage Examples

You can check out our tests section to see a bunch of different usage examples.


Small and simple http server for mocking and asserting http calls




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