Can Silktide test password-protected websites?

Yes. How you set it up depends on the protection:

HTTP authentication

If the browser shows a username/password pop-up before the page loads, that is HTTP authentication. Admins can enter those credentials when adding the website, or later under website settings. See Advanced settings.

If people log in through a normal form on the page, Silktide can be taught to complete that form. That is configured as authentication for the website (and may need help from Silktide depending on complexity).

Silktide cannot complete CAPTCHAs or multi-factor authentication codes. Use a dedicated test account with minimal privileges, and avoid environments where crawler clicks could change real customer data.

Related: user flows are for journeys after login (forms, wizards), not for the login itself.