test: add test case

Author: auvred

Diff for: packages/runtime-core/__tests__/vnode.spec.ts

@@ -63,6 +63,17 @@ describe('vnode', () => {
     })
   })
 
+  test('create from an existing text vnode', () => {
+    const vnode1 = createVNode('div', null, 'text', PatchFlags.TEXT)
+    const vnode2 = createVNode(vnode1)
+    expect(vnode2).toMatchObject({
+      type: 'div',
+      patchFlag: PatchFlags.BAIL,
+      children: 'text',
+      shapeFlag: ShapeFlags.ELEMENT | ShapeFlags.TEXT_CHILDREN
+    })
+  })
+
   test('vnode keys', () => {
     for (const key of ['', 'a', 0, 1, NaN]) {
       expect(createVNode('div', { key }).key).toBe(key)