Update error message (vuejs#761)

Author: mya-ake

packages/test-utils/src/wrapper.js

@@ -664,8 +664,10 @@ export default class Wrapper implements BaseWrapper {
         data[key] === this.vm[key]
       ) {
         throwError(
-          `wrapper.setProps() called with ${key} property ` +
-          `needs to create a new Object`
+          `wrapper.setProps() called with the same object ` +
+          `of the existing ${key} property. ` +
+          `You must call wrapper.setProps() with a new object ` +
+          `to trigger reactivity`
         )
       }
 

test/specs/wrapper/setProps.spec.js

@@ -192,7 +192,7 @@ describeWithShallowAndMount('setProps', mountingMethod => {
       }
     })
 
-    const message = '[vue-test-utils]: wrapper.setProps() called with obj property needs to create a new Object'
+    const message = '[vue-test-utils]: wrapper.setProps() called with the same object of the existing obj property. You must call wrapper.setProps() with a new object to trigger reactivity'
     const fn = () => wrapper.setProps({ obj })
     expect(fn)
       .to.throw()