Can a Keypass file theoretically be cracked offline?

So you create a .kbdx file, protected by a password.

AFAIK in asymmetric key schemes and in WPA-AES brute-forcing consists of:

  • try a random password on the private key / on the router
  • if it doesn’t log you in, try another.

So you immediately know did you hit the correct password.

What about a password manager’s database? You know nothing about the content of the file. How do you know you did manage to crack it?