nise-defake-issue

Start server

npm start

Repro Issue

When using FakeXMLHttpRequest in Sinon, useFilters can be used to bypass fake XHR for configured urls. This is achieved by the defake function in nise that maps important functions between the fake XHR and XmlHttpRequest. defake is called in open.

However, since user still holds the instance of FakeXMLHttpRequest instead of XmlHttpRequest. Modifications to it are not propagated to the real XHR behind. This can sometimes cause issue.

Minimal Example

sinon.FakeXMLHttpRequest.useFilters = true;
sinon.FakeXMLHttpRequest.addFilter(() => true);

const server = sinon.fakeServer.create();

const xhr = new XMLHttpRequest();
xhr.open("GET", "http://www.mocky.io/v2/5e8aa67e2d00003c1a1a473e", true);
xhr.withCredentials = true;
xhr.send();

The actual XHR does not have withCredentials set to true.