fix(setprops): allowed for setProps to be synced with nextTick intervals

setProps in certain cases was being blown away by nextTick intervals. If the property is not up to
date, setProps will be called again to sync the changes.

fix #1419

Author: AtofStryker

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

@@ -711,7 +711,15 @@ export default class Wrapper implements BaseWrapper {
 
       // $FlowIgnore : Problem with possibly null this.vm
       this.vm.$forceUpdate()
-      return nextTick()
+      return new Promise((resolve, reject) => {
+        nextTick().then(() => {
+          const isUpdated = Object.keys(data).some(key => {
+            // $FlowIgnore : Problem with possibly null this.vm
+            return this.vm[key] === data[key]
+          })
+          return !isUpdated ? this.setProps(data).then(resolve()) : resolve()
+        })
+      })
     } catch (err) {
       throw err
     } finally {

Diff for: test/specs/wrapper/setProps.spec.js

@@ -187,6 +187,33 @@ describeWithShallowAndMount('setProps', mountingMethod => {
       await wrapper.setProps({ prop1 })
       expect(wrapper.vm.prop2).to.equal(prop1)
     })
+
+    it('invokes watchers with immediate set to "true" when ', async () => {
+      const callback = sinon.spy()
+      const TestComponent = {
+        template: '<div />',
+        props: ['propA'],
+        mounted() {
+          this.$watch(
+            'propA',
+            function() {
+              callback()
+            },
+            { immediate: true }
+          )
+        }
+      }
+      const wrapper = mountingMethod(TestComponent, {
+        propsData: { propA: 'none' }
+      })
+
+      expect(callback.calledOnce)
+      callback.resetHistory()
+
+      await wrapper.setProps({ propA: 'value' })
+      expect(wrapper.props().propA).to.equal('value')
+      expect(callback.calledOnce)
+    })
   })
 
   it('props and setProps should return the same reference when called with same object', () => {