Fakify is a tiny library used to stub, fake or spy on default exported functions in Javascript.
Fakify can be used to stub Commonjs/ES6 modules either native Node or custom modules.
Fakify can be used with Sinon, Mocha, Chai.
npm install fakify
Let consider you have a sum function that do this:
// sum.js module
function sum(x, y) {
return x + y;
}
// Notice sum is exported as default function
module.exports = sum;
... and you want to import and use it as follows:
const sum = require('./sum');
function doStuff(x, y) {
// do some stuff then ...
return sum(x, y);
}
module.exports = doStuff;
... here is how to stub the sum function
const fakify = require('fakify');
const fakeSum = sinon.stub().returns(5);
const sut = fakify('./doStuff', {
'./sum': fakeSum,
});
sut(1, 2);
sinon.assert.calledOnce(fakeSum);
sinon.assert.calledWithExactly(fakeSum, 1, 2);
Fakify can be used to stub more than one dependency at a time as follows:
const sut = fakify('./doStuff', {
'./sum': sinon.stub().returns(5),
'./sub': sinon.stub({ sub }, 'sub').callThrough(),
});