assertThrows(IllegalArgumentException.class, () -> InputValidator.validateUsername(username));
    }

    @Test
    @DisplayName("Test username length validation")
    void testUsernameLengthValidation() {
        String longUsername = "a".repeat(InputValidator.MAX_USERNAME_LENGTH + 1);
        assertThrows(IllegalArgumentException.class, () -> InputValidator.validateUsername(longUsername));
    }