Can't use [email protected] with vue 2.7 script setup

[arthurrmp]

Subject of the issue

When using [email protected] with [email protected], I'm not able to test SFC components made with script setup syntactic sugar.

Steps to reproduce

1. Created a new project using vue-cli (vue 2)
2. update the Vue version: yarn install [email protected]
3. create any component with script setup syntactic sugar
4. try to add any unit test to this component

Expected behaviour

It should pass the simple test.

Actual behaviour

// App.vue
<template>
  <div id="app">
    <h1>{{ msg }}</h1>
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  setup() {
    const msg = "new message";
    return {
      msg,
    };
  },
});
</script>

// AppScriptSetup.vue
<template>
  <div id="app">
    <h1>{{ msg }}</h1>
  </div>
</template>

<script lang="ts" setup>
const msg = "new message";
</script>

import { shallowMount } from "@vue/test-utils";
import App from "@/App.vue";
import AppScriptSetup from "@/AppScriptSetup.vue";

describe("App.vue", () => {
  it("renders the App", () => {
    const msg = "new message";
    const wrapper = shallowMount(App);
    expect(wrapper.text()).toBe(msg); // This works as expected 
  });
});

describe("AppScriptSetup.vue", () => {
  it("renders the AppScriptSetup", () => {
    const msg = "new message";
    const wrapper = shallowMount(AppScriptSetup);
    expect(wrapper.text()).toBe(msg); // This fails with the error: [Vue warn]: Property or method "msg" is not defined on the instance but referenced during render.
  });
});

Open a terminal and run yarn test:unit at https://codesandbox.io/p/github/arthurrmp/vue-2-script-setup-test-utils to see it live.
The same code works as intended using Vue 3, as seen at https://codesandbox.io/p/github/arthurrmp/vue-3-script-setup-test-utils

Possible Solution

I've not been able to find any alternatives.

[arthurrmp]

duplicated of #1983