Vue-test-utils: using $nextTick multiple times in a single test

Question

I'm writing unit tests for vuelidate validation in my component. I figured out that the $touch() method is called asynchronously, so I need to use $nextTick() for the expect() . The problem appears when I need two nextTick()s for two expect()s .

describe('Validations', () => {
    let data
    let myComponent
    beforeEach(() => {
        data = () => {
            propertyABC = 'not allowed value'
        }
        myComponent = localVue.component('dummy', {template: '<div></div>', validations, data})

    it('Properly validates propertyABC', (done) => {
        Vue.config.errorHandler = done
        let wrapper = mount(myComponent, {localVue})
        wrapper.vm.$v.$touch()

        wrapper.vm.$nextTick(() => {
            expect(wrapper.vm.$v.propertyABC.$error).to.be.true
            # fails, because propertyABC === 'allowed value', adn thus $error is false
            done()
        }

        wrapper.vm.propertyABC = 'allowed value'
        wrapper.vm.$v.propertyABC.$touch()

        wrapper.vm.$nextTick(() => {
            expect(wrapper.vm.$v.proprtyABC.$error).to.be.false
            done()
        }
    })
})

How can I run this test without splitting it into two separate tests? I think nesting the $nextTick() might work, but it would be not flexible for higher amount of tests.

Answer 1

If you're able to use async functions , then you could await the $nextTick calls. This would avoid having to nest them and would keep everything in the same test.

Like so:

describe('Validations', () => {
  let data;
  let myComponent;
  beforeEach(() => {
    data = () => ({ propertyABC = 'not allowed value' });
    myComponent = localVue.component('dummy', {template: '<div></div>', validations, data});
  });

  it('Properly validates propertyABC', async  () => {
    let wrapper = mount(myComponent, {localVue});
    wrapper.vm.$v.$touch();

    await wrapper.vm.$nextTick();

    expect(wrapper.vm.$v.propertyABC.$error).to.be.true;

    wrapper.vm.propertyABC = 'allowed value';
    wrapper.vm.$v.propertyABC.$touch();

    await wrapper.vm.$nextTick();

    expect(wrapper.vm.$v.proprtyABC.$error).to.be.false;
  })
})

Answer 2

Another approach is to use flushPromises.

import flushPromises from 'flush-promises';
...

test('some async test', async () => {
  const wrapper = mount(MyComponent, { localVue });
  wrapper.vm.$v.$touch();
  await flushPromises();
});

flushPromises() returns a promise itself, so its useful when you need/want to chain things using .then().then() etc...