Update check for rendered components

Author: alexeyr

k6/root.js

@@ -8,6 +8,17 @@ export default () => {
   const rootUrl = url('');
   check(http.get(rootUrl), {
     'status was 200': (res) => res.status === 200,
-    'includes expected text': (res) => res.body?.toString()?.includes('Hello WORLD!'),
+    'renders components successfully': (res) => {
+      const body = res.html().text();
+      return Object.entries({
+        // This is visible on the page in the browser 4 times, but for some reason, the one under
+        // "Server Rendered React Component Without Redux" is missing in `body`.
+        'Hello, Mr. Server Side Rendering!': 3,
+        'Hello, Mrs. Client Side Rendering!': 2,
+        'Hello, Mrs. Client Side Hello Again!': 1,
+        'Hello ES5, Mrs. Client Side Rendering!': 1,
+        'Hello WORLD! Will this work?? YES! Time to visit Maui': 1,
+      }).every(([text, count]) => body.split(text).length >= count + 1);
+    },
   });
 };