test: add tests

packages/vue/__tests__/e2e/memory-leak.spec.ts

@@ -143,4 +143,85 @@ describe('not leaking', async () => {
     },
     E2E_TIMEOUT,
   )
+
+  // https://github.com/element-plus/element-plus/issues/21408
+  test(
+    'cached text nodes in Fragment should not retaining detached DOM nodes',
+    async () => {
+      const client = await page().createCDPSession()
+      await page().evaluate(async () => {
+        const { createApp, ref } = (window as any).Vue
+        createApp({
+          components: {
+            Comp: {
+              template: `<div>{{ test.length }}</div>`,
+              setup() {
+                const test = ref([...Array(3000)].map((_, i) => ({ i })))
+                // @ts-expect-error
+                window.__REF__ = new WeakRef(test)
+
+                return { test }
+              },
+            },
+          },
+          template: `
+          <button id="addBtn" @click="add">add</button>
+          <button id="toggleBtn" @click="click">button</button>
+          <div v-if="toggle">
+            <template v-for="item in items" :key="item">
+              text
+              <div>{{ item }}</div>
+            </template>
+            <Comp/>
+          </div>
+        `,
+          setup() {
+            const toggle = ref(true)
+            const items = ref([1])
+            const click = () => (toggle.value = !toggle.value)
+            const add = () => items.value.push(2)
+            return { toggle, click, items, add }
+          },
+        }).mount('#app')
+      })
+
+      expect(await html('#app')).toBe(
+        `<button id="addBtn">add</button>` +
+          `<button id="toggleBtn">button</button>` +
+          `<div>` +
+          ` text ` +
+          `<div>1</div>` +
+          `<div>3000</div></div>`,
+      )
+
+      await click('#addBtn')
+      expect(await html('#app')).toBe(
+        `<button id="addBtn">add</button>` +
+          `<button id="toggleBtn">button</button>` +
+          `<div>` +
+          ` text ` +
+          `<div>1</div>` +
+          ` text ` +
+          `<div>2</div>` +
+          `<div>3000</div></div>`,
+      )
+
+      await click('#toggleBtn')
+      expect(await html('#app')).toBe(
+        `<button id="addBtn">add</button>` +
+          `<button id="toggleBtn">button</button><!--v-if-->`,
+      )
+
+      const isCollected = async () =>
+        // @ts-expect-error
+        await page().evaluate(() => window.__REF__.deref() === undefined)
+
+      while ((await isCollected()) === false) {
+        await client.send('HeapProfiler.collectGarbage')
+      }
+
+      expect(await isCollected()).toBe(true)
+    },
+    E2E_TIMEOUT,
+  )
 })