How to write a test that expects an error to be issued in java

I am testing this feature:

fun findByUsername(username: String): Account {
        return accountRepo.findByUsername(username).orElseThrow {
            UsernameNotFoundException("Username was not found")
        }
    }

here is my test

@Test
    fun checkFindByUsername() {
        val userRegistrationForm = UserRegistrationForm("testUser3", "123", "eee", false)
        val user = accountService.createAccount(userRegistrationForm)

        assertEquals(accountRepo.findByUsername("").orElseThrow {
            UsernameNotFoundException("Username was not found")
        }, "Username was not found")
    }

what to do to make the test pass? Do you need to use any specific assertion? sorry, understand that stupid question