How to test computed properties in Vue.js? Can't mock "data"

Okay. I've found a dumb solution. Dumb but works.

You have been warned =)

The idea: To use .call({}) to replace this inside that calls:

it('should remove duplicates from array', () => {  const mockSource = {     source: [1, 2, 1, 2, 3],     getUniq (arr) {       return FiltersList.methods.removeDuplicates(arr)     }  }  const result = FiltersList.computed.types.call(mockSource)  const expectedLength = 3  expect(result).to.have.length(expectedLength)})

So basically you can specify your own this with any kind of data.and call YourComponent.computed.foo.call(mockSource). Same for methods

Just change the variable from which depends computed property and expect it.

This is my work example for component computed prop:

import Vue from 'vue'import Zoom from 'src/components/Zoom'import $ from 'jquery'/* eslint-disable no-unused-vars *//** * get template for wrapper Vue object make Vue with Zoom component and that template * @param wrapperTemplate * @returns {Vue$2} */const makeWrapper = (wrapperTemplate = '<div><zoom ref="component"></zoom></div>') => {  return new Vue({    template: wrapperTemplate,    components: {Zoom}  })}const startWrapperWidth = 1093const startWrapperHeight = 289const startImageWidth = 1696const startImageHeight = 949const padding = 15/** * gets vueWrapper and return component from it * @param vueWrapper * @param useOffset * @returns {'Zoom component'} */const setSizesForComponent = (vueWrapper) => {  vueWrapper.$mount()  var cmp = vueWrapper.$refs.component  var $elWrapper = $(cmp.$el)  var $elImage = $elWrapper.find(cmp.selectors.image)  $elWrapper.width(startWrapperWidth)  $elWrapper.height(startWrapperHeight)  $elWrapper.css({padding: padding})  $elImage.width(startImageWidth)  $elImage.height(startImageHeight)  cmp.calculateSizesAndProportions()  return cmp}describe('onZoom method (run on mousemove)', () => {  sinon.spy(Zoom.methods, 'onZoom')  let vueWrapper = makeWrapper()  let cmp = setSizesForComponent(vueWrapper)  let e = document.createEvent('HTMLEvents')  e.initEvent('mousemove', true, true)  e.pageX = 150  e.pageY = 250  let callsOnZoomBeforeMousemove = Zoom.methods.onZoom.callCount  cmp.$el.dispatchEvent(e)  describe('left and top computed props', () => {    it('left', () => {      expect(cmp.left).is.equal(-74)    })    it('top', () => {      expect(cmp.top).is.equal(-536)    })  })})