Login form: you enter a valid username/password, click login, and nothing visually happens. How would you investigate this and what could be the cause?

If nothing visually happens when entering a valid login and password and clicking the "Login" button, an investigation should be conducted in several directions:

1. Checking network requests:

   • Open developer tools in the browser (F12) and go to the Network tab.
   • Click "Login" and see if a request is sent to the server.
   • If no request is sent, the problem might be in JavaScript (e.g., the event does not trigger).
   • If a request is sent, check the server response: errors, status, response body.

2. Checking the browser console:

   • JavaScript errors can block further script execution.
   • If there are errors, they need to be fixed.

3. Checking form validation:

   • The form might not pass client-side validation, and the button does not send data.

4. Checking the UI:

   • It might be that after a successful login, a redirect or state update occurs, but the UI does not update due to rendering bugs.

5. Server logging:

   • Check if the server receives the request and how it processes it.

6. Checking application state:

   • If using SPA, check the authorization state and routing.

Thus, the problem could be caused by:

• JavaScript errors blocking processing.
• No request being sent due to handler issues.
• Server errors returning an unclear response.
• UI update problems after successful login.

The investigation starts with developer tools and logs to localize the problem.