[test] Output warnings in the rendered components

test/regressions/index.test.js

@@ -51,6 +51,14 @@ async function main() {
   // prepare screenshots
   await fse.emptyDir(screenshotDir);
 
+  let errorMessage;
+
+  page.on('console', async (msg) => {
+    if (msg.args().length > 0 && (msg.type() === 'error' || msg.type() === 'warning')) {
+      errorMessage = Promise.all(msg.args().map((x) => x.jsonValue()));
+    }
+  });
+
   describe('visual regressions', () => {
     after(async () => {
       await browser.close();
@@ -77,6 +85,12 @@ async function main() {
         await fse.ensureDir(path.dirname(screenshotPath));
         // Testcase.screenshot would resize the viewport to the element bbox.
         await page.screenshot({ clip, path: screenshotPath, type: 'png' });
+
+        if (errorMessage) {
+          const msg = await errorMessage;
+          errorMessage = undefined;
+          console.warn(msg);
+        }
       });
     });
   });