Write about propsData

[lmiller1990]

https://github.com/lmiller1990/vue-testing-handbook/blob/master/docs/components-with-props.md

Write about propsData. Some ideas:

• component receives and renders a prop. Show how to test that. Better yet, write the test first, and then the component, using the error messages to guide your development
• factory functions. Often you end up with tests like this:

describe("Foo", () => {
  it("something", () => {
    const wrapper = mount(Foo, {
      propsData: {
        shouldShow: true,
        bar: 'foo'
    })
  })

 it("another thing", () => {
    const wrapper = mount(Foo, {
      propsData: {
        shouldShow: false,
        bar: 'foo'
    })
  })
})

We can introduce a factory function:

const factory = (propsData) => {
  return mount(Foo, {
    propsData: {
      bar: "foo",
      ...propsData
    }
  })
}

const wrapper = factory({ shouldShow: false })

const wrapper = factory({ shouldShow: true })