chore: add repro

tests/components/LastUpdated.vue

@@ -0,0 +1,12 @@
+<template>
+  <div class="last-updated" v-if="when">
+    Last update: <span>{{ when }}</span>
+  </div>
+</template>
+
+<script>
+export default {
+  name: "last-updated",
+  props: ["when"]
+}
+</script>

tests/unmount.spec.ts

@@ -1,4 +1,5 @@
 import { defineComponent } from 'vue'
+import LastUpdated from './components/LastUpdated.vue'
 
 import { mount } from '../src'
 
@@ -41,4 +42,20 @@ describe('Unmount', () => {
     wrapper.unmount()
     expect(errorHandler).not.toHaveBeenCalled()
   })
+
+  it("The LastUpdated component renders the 'when' property", async () => {
+    const wrapper = mount(LastUpdated, { props: { when: 'today' } })
+
+    await wrapper.vm.$nextTick()
+    expect(wrapper.html()).toContain('<span>today</span>')
+    wrapper.unmount()
+  })
+
+  it("The LastUpdated component doesn't render when 'when' is undefined", async () => {
+    const wrapper = mount(LastUpdated, { props: { when: undefined } })
+
+    await wrapper.vm.$nextTick()
+    expect(wrapper.html()).not.toContain('<span>today</span>')
+    wrapper.unmount()
+  })
 })