Closes #72: Change the way we load the page for LCP (#75)

src/support/steps/lcp-beacon-script.ts

@@ -52,8 +52,11 @@ Given('I visit the following urls in {string}', async function (this: ICustomWor
     for (const row of data) {
         const url: string = `${WP_BASE_URL}/${row[0]}`;
         await this.utils.visitPage(row[0]);
-        // Wait for 2 seconds before fetching from DB.
-        await this.page.waitForTimeout(2000);
+        // Wait the beacon to add an attribute `beacon-complete` to true before fetching from DB.
+        await this.page.waitForFunction(() => {
+            const beacon = document.querySelector('[data-name="wpr-lcp-beacon"]');
+            return beacon && beacon.getAttribute('beacon-completed') === 'true';
+        });
 
         // Get the LCP/ATF from the DB
         sql = `SELECT lcp, viewport FROM ${tablePrefix}wpr_above_the_fold WHERE url LIKE "%${row[0]}%"`;