RunKit + npm: sinon

const _ = require('lodash') const sinon = require('sinon@2.0.0-pre.4') , match = sinon.match , __ = match.any

const id = Symbol('id') , Node = class {} function rand(){ return _.random(0, Number.MAX_SAFE_INTEGER).toString() } var foo = new Node(); foo[id] = rand() var bar = new Node(); bar[id] = rand()

const filter = sinon.stub() filter.returns(true) filter.withArgs(foo).returns(false)

filter(foo)

filter(bar)