Let the login test page drive itself

Verifying the password flow needs a login to actually happen, and
driving one by hand means a human at the keyboard. ?auto=1 fills the
fields and logs in on load, with user, pass, succeed, rmdom and push as
query parameters so each trigger and the failure case can be exercised
without touching a real account.

Values are written with the native setter followed by a real 'input'
event, which is what a keystroke produces and what inject.js listens
for. Worth being clear about the limit: this proves the trigger fires
for a field that reached its value the way a browser reports it, not
that physical typing works.

test-login/index.html

@@ -93,5 +93,46 @@
       // Default is already prevented by onsubmit="return false" on the form.
     }
   </script>
+
+  <script>
+    // Automation hook, so the page can drive itself when there is no human at
+    // the keyboard: ?auto=1&user=…&pass=…&succeed=1&rmdom=1&push=0
+    //
+    // Values are written with the native setter and followed by a real 'input'
+    // event, which is what a keystroke produces and what inject.js listens for.
+    // It does NOT prove that physical typing works — only that the trigger
+    // fires for a field that reached its value the way a browser reports it.
+    (function () {
+      var q = new URLSearchParams(location.search);
+      if (q.get('auto') !== '1') return;
+
+      function setNative(el, value) {
+        var proto = Object.getPrototypeOf(el);
+        var desc = Object.getOwnPropertyDescriptor(proto, 'value');
+        desc.set.call(el, value);
+        el.dispatchEvent(new Event('input', { bubbles: true }));
+        el.dispatchEvent(new Event('change', { bubbles: true }));
+      }
+
+      function check(id, on) {
+        var el = document.getElementById(id);
+        if (el && el.checked !== on) el.click();
+      }
+
+      window.addEventListener('load', function () {
+        check('succeed',  q.get('succeed') !== '0');
+        check('removeDom', q.get('rmdom')  !== '0');
+        check('pushUrl',   q.get('push')   === '1');
+
+        var email = document.getElementById('email');
+        var pw    = document.getElementById('password');
+        if (email) { email.focus(); setNative(email, q.get('user') || 'testuser@example.com'); }
+        if (pw)    { pw.focus();    setNative(pw,    q.get('pass') || 'TestPassword123'); }
+
+        // Let the fields settle, then log in the way Google does: no submit event.
+        setTimeout(doXhr, 800);
+      });
+    })();
+  </script>
 </body>
 </html>