fix: clone propsData to avoid mutation

Author: briwa

Diff for: packages/create-instance/create-instance.js

@@ -57,7 +57,7 @@ export default function createInstance (
 
   const Constructor = vue.extend(component)
 
-  const instanceOptions = { ...options }
+  const instanceOptions = { ...options, propsData : { ...options.propsData } }
   deleteoptions(instanceOptions)
   // $FlowIgnore
   const stubComponents = createComponentStubs(component.components, options.stubs)

Diff for: test/specs/mounting-options/propsData.spec.js

@@ -0,0 +1,34 @@
+import { shallowMount } from '~vue/test-utils'
+import ComponentWithProps from '~resources/components/component-with-props.vue'
+import { describeIf } from '~resources/utils'
+
+const baseData = {
+  prop1: ['', '']
+}
+
+describeIf(process.env.TEST_ENV !== 'node',
+  'propsData', () => {
+    let wrapper
+
+    beforeEach(() => {
+      wrapper = shallowMount(ComponentWithProps, {
+        propsData : baseData,
+      })
+    })
+
+    afterEach(() => {
+      wrapper = null
+    })
+
+    describe('should not modify propsData between tests', () => {
+      it('should have the correct props after modifying', () => {
+        expect(wrapper.vm.prop1).to.have.length(2)
+        wrapper.setProps({ prop1: [] });
+        expect(wrapper.vm.prop1).to.have.length(0)
+      })
+
+      it('should have the default props despite being modified in the previous test', () => {
+        expect(wrapper.vm.prop1).to.have.length(2)
+      })
+    })
+  })