test: fix mixin case

packages/runtime-core/src/component.ts

@@ -145,6 +145,7 @@ class InternalComponent implements PublicInstanceMethods {
       // so that the extended class constructor (and property initializers) can
       // access $props.
       this.$props = props
+      Object.assign(this, props)
     }
     if (__COMPAT__) {
       ;(this as any)._eventEmitter = new EventEmitter(this)

packages/runtime-core/src/componentProps.ts

@@ -47,11 +47,9 @@ export function initializeProps(
   // expose initial props on the raw instance so that they can be accessed
   // in the child class constructor by class field initializers.
   if (options != null) {
-    for (const key in props) {
     // it's okay to just set it here because props options are normalized
     // and reserved keys should have been filtered away
-      ;(instance as any)[key] = props[key]
-    }
+    Object.assign(instance, props)
   }
 }
 

packages/runtime-core/src/componentState.ts

@@ -20,12 +20,11 @@ export function extractInitializers(
   data: any = {}
 ): any {
   const keys = Object.keys(instance)
-  const props = instance.$options.props
+  const props = instance.$props
   for (let i = 0; i < keys.length; i++) {
     const key = keys[i]
     if (!isReservedKey(key)) {
-      // it's possible for a prop to be present here when it's declared
-      if (!props || !props.hasOwnProperty(key)) {
+      if (!props.hasOwnProperty(key)) {
         data[key] = (instance as any)[key]
       }
     }