feat: export createWrapper method to create wrapper from instance (vuejs#868)

Author: eddyerburgh

Diff for: docs/api/README.md

@@ -6,4 +6,5 @@
 !!!include(docs/api/renderToString.md)!!!
 !!!include(docs/api/selectors.md)!!!
 !!!include(docs/api/createLocalVue.md)!!!
+!!!include(docs/api/createWrapper.md)!!!
 !!!include(docs/api/config.md)!!!

Diff for: docs/api/createWrapper.md

@@ -0,0 +1,19 @@
+## createWrapper()
+
+- **Returns:**
+  - `{Wrapper}`
+
+- **Usage:**
+
+`createWrapper` creates a `Wrapper` for a mounted Vue instance, or an HTML element.
+
+```js
+import { createWrapper } from '@vue/test-utils'
+import Foo from './Foo.vue'
+
+const Constructor = Vue.extend(Foo)
+const vm = new Constructor().$mount()
+const wrapper = createWrapper(vm)
+expect(wrapper.vm.foo).toBe(true)
+```
+

Diff for: flow/wrapper.flow.js

@@ -46,6 +46,6 @@ declare interface BaseWrapper {
 
 declare type WrapperOptions = {
   // eslint-disable-line no-undef
-  attachedToDocument: boolean,
+  attachedToDocument?: boolean,
   sync?: boolean
 };

Diff for: packages/test-utils/src/create-wrapper.js

@@ -6,7 +6,7 @@ import VueWrapper from './vue-wrapper'
 
 export default function createWrapper (
   node: VNode | Component,
-  options: WrapperOptions
+  options: WrapperOptions = {}
 ): VueWrapper | Wrapper {
   const componentInstance = node.componentInstance || node.child
   if (componentInstance) {

Diff for: packages/test-utils/src/index.js

@@ -4,6 +4,7 @@ import createLocalVue from './create-local-vue'
 import TransitionStub from './components/TransitionStub'
 import TransitionGroupStub from './components/TransitionGroupStub'
 import RouterLinkStub from './components/RouterLinkStub'
+import createWrapper from './create-wrapper'
 import Wrapper from './wrapper'
 import WrapperArray from './wrapper-array'
 import config from './config'
@@ -19,6 +20,7 @@ function shallow (component, options) {
 
 export default {
   createLocalVue,
+  createWrapper,
   config,
   mount,
   shallow,

Diff for: test/specs/create-wrapper.spec.js

@@ -0,0 +1,15 @@
+import Vue from 'vue'
+import { createWrapper, Wrapper, WrapperArray } from '~vue/test-utils'
+import Component from '~resources/components/component.vue'
+import { describeRunIf } from 'conditional-specs'
+
+describeRunIf(process.env.TEST_ENV !== 'node', 'mount', () => {
+  it.only('exports createWrapper', () => {
+    const Constructor = Vue.extend(Component)
+    const vm = new Constructor().$mount()
+    const wrapper = createWrapper(vm)
+    expect(wrapper.is(Component)).to.equal(true)
+    expect(wrapper).instanceof(Wrapper)
+    expect(wrapper.findAll('div')).instanceof(WrapperArray)
+  })
+})