Add test for functional component using render function

Author: jesusgn90

e2e/__projects__/basic/components/FunctionalSFCRender.vue

@@ -0,0 +1,17 @@
+<script>
+export default {
+  name: 'FunctionalSFCRender',
+  functional: true,
+  render(createElement, { $style }) {
+    return createElement('div', {
+      class: [$style.ModuleClass]
+    })
+  }
+}
+</script>
+
+<style lang="scss" module>
+.ModuleClass {
+  width: auto;
+}
+</style>

e2e/__projects__/basic/test.js

@@ -6,6 +6,7 @@ import jestVue from 'vue-jest'
 import RenderFunction from './components/RenderFunction.vue'
 import Jade from './components/Jade.vue'
 import FunctionalSFC from './components/FunctionalSFC.vue'
+import FunctionalSFCRender from './components/FunctionalSFCRender.vue'
 import Basic from './components/Basic.vue'
 import BasicSrc from './components/BasicSrc.vue'
 import { randomExport } from './components/NamedExport.vue'
@@ -92,6 +93,12 @@ test('processes functional components', () => {
   expect(clickSpy).toHaveBeenCalledWith(1)
 })
 
+test('processes functional components using render function', () => {
+  const wrapper = mount(FunctionalSFCRender)
+  const CSS_CLASSES = ['ModuleClass']
+  expect(wrapper.classes().toString()).toBe(CSS_CLASSES.toString())
+})
+
 test('processes SFC with functional template from parent', () => {
   const wrapper = mount(FunctionalSFCParent)
   expect(wrapper.text().trim()).toBe('foo')