test(e2e): add e2e test for commits example (#526)

* test(e2e): add e2e test for commits example

* test(e2e): add waitForResponse to enhance the test

* test(e2e): use mocks for commits test

packages/vue/examples/composition/commits.html

@@ -1,4 +1,5 @@
 <script src="../../dist/vue.global.js"></script>
+<script src="../mocks/commits.js"></script>
 
 <div id="demo">
   <h1>Latest Vue.js Commits</h1>
@@ -37,10 +38,17 @@ const App = {
     const currentBranch = ref('master')
     const commits = ref(null)
 
-    watch(() => {
-      fetch(`${API_URL}${currentBranch.value}`)
-        .then(res => res.json())
-        .then(data => { commits.value = data })
+    watch([currentBranch, commits], () => {
+      if (window.location.hash === '#test') {
+        // use mocks in e2e to avoid dependency on network / authentication
+        setTimeout(() => {
+          commits.value = window.MOCKS[currentBranch.value]
+        }, 0)
+      } else {
+        fetch(`${API_URL}${currentBranch.value}`)
+          .then(res => res.json())
+          .then(data => { commits.value = data })
+      }
     })
 
     return {