In Vue.js, a functional component can return multiple root nodes by using a render function that returns an array of createdElements.
export default {
functional: true,
props: ['cellData'],
render: function (h, context) {
return [
h('td', context.props.cellData.category),
h('td', context.props.cellData.description)
]
}
}
This works great but I'm having trouble trying to create a unit test for such a component. Using shallowMount on the component results in [Vue warn]: Multiple root nodes returned from render function. Render function should return a single root node.
import { shallowMount } from '@vue/test-utils'
import Cell from '@/components/Cell'
wrapper = shallowMount(Cell, {
context: {
props: {
cellData {
category: 'foo',
description: 'bar'
}
}
}
});
This github issue suggests that the component needs to be wrapped in a single root node to actually render it, but trying that results in [vue-test-utils]: mount.context can only be used when mounting a functional component
import { shallowMount } from '@vue/test-utils'
import Cell from '@/components/Cell'
wrapper = shallowMount('<div><Cell></div>', {
context: {
props: {
cellData {
category: 'foo',
description: 'bar'
}
}
}
});
So how do I test a functional component that returns multiple root nodes?
You could create a higher order, transparent wrapper component that passes all props and event listeners to the inner Cell component using v-bind="$attrs"[1] and v-on="$listeners"[2]. Then you can use propsData to pass props to the wrapper component ..
import { mount } from '@vue/test-utils'
import Cell from '@/components/Cell'
const WrappedCell = {
components: { Cell },
template: `
<div>
<Cell v-bind="$attrs" v-on="$listeners" />
</div>
`
}
const wrapper = mount(WrappedCell, {
propsData: {
cellData: {
category: 'foo',
description: 'bar'
}
}
});
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