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));
    }

    @ParameterizedTest

    }

    /**
     * Validates username
     *
     * @param username the username to validate
     * @throws IllegalArgumentException if username is invalid
     */
    public static void validateUsername(String username) {
        if (username == null) {
            return; // Null username allowed for anonymous
        }
        if (username.length() > MAX_USERNAME_LENGTH) {