Allow mocks to be set in config object

docs/en/api/config.md

@@ -24,3 +24,22 @@ import VueTestUtils from '@vue/test-utils'
 
 VueTestUtils.config.stubs['my-component'] = '<div />'
 ```
+
+### `mocks`
+
+- type: `Object`
+- default: `{}`
+
+Like `stubs`, the values passed to `config.mocks` are used by default. Any values passed to the mounting options `mocks` object will take priority over the ones declared in `config.mocks`.
+
+Example:
+
+```js
+import VueTestUtils from '@vue/test-utils'
+
+VueTestUtils.config.mocks['$store'] = {
+  state: {
+    id: 1
+  }
+}
+```

packages/shared/merge-options.js

@@ -1,16 +1,16 @@
 // @flow
 
-function getStubs (optionStubs, config) {
-  if (optionStubs ||
-    (config.stubs && Object.keys(config.stubs).length > 0)) {
-    if (Array.isArray(optionStubs)) {
+function getOptions (key, options, config) {
+  if (options ||
+    (config[key] && Object.keys(config[key]).length > 0)) {
+    if (Array.isArray(options)) {
       return [
-        ...optionStubs,
-        ...Object.keys(config.stubs || {})]
+        ...options,
+        ...Object.keys(config[key] || {})]
     } else {
       return {
-        ...config.stubs,
-        ...optionStubs
+        ...config[key],
+        ...options
       }
     }
   }
@@ -22,6 +22,8 @@ export function mergeOptions (
 ): Options {
   return {
     ...options,
-    stubs: getStubs(options.stubs, config)
+    stubs: getOptions('stubs', options.stubs, config),
+    mocks: getOptions('mocks', options.mocks, config)
   }
 }
+

packages/test-utils/src/config.js

@@ -5,5 +5,6 @@ export default {
   stubs: {
     transition: TransitionStub,
     'transition-group': TransitionGroupStub
-  }
+  },
+  mocks: {}
 }

test/specs/config.spec.js

@@ -2,7 +2,8 @@ import {
   mount,
   config,
   TransitionStub,
-  TransitionGroupStub
+  TransitionGroupStub,
+  createLocalVue
 } from '~vue/test-utils'
 
 describe('config', () => {
@@ -33,6 +34,29 @@ describe('config', () => {
     expect(wrapper.contains(TransitionGroupStub)).to.equal(true)
   })
 
+  it('mocks a global variable', () => {
+    const localVue = createLocalVue()
+    const t = 'real value'
+    localVue.prototype.$t = t
+
+    const testComponent = {
+      template: `
+        <div>{{ $t }}</div>
+      `
+    }
+
+    config.mocks['$t'] = 'mock value'
+
+    const wrapper = mount(testComponent, {
+      localVue, t
+    })
+
+    expect(wrapper.vm.$t).to.equal('mock value')
+    expect(wrapper.text()).to.equal('mock value')
+
+    localVue.prototype.$t = undefined
+  })
+
   it('doesn\'t stub transition when config.stubs.transition is set to false', () => {
     const testComponent = {
       template: `