An insurer doing business globally wants to use a validation expression to verify that a...

In Guidewire InsuranceSuite configuration,Validation Expressions(found in the Data Model within entity properties or specialized validation files) follow a specific logic: they must returnnullif the data is valid, and anon-null value(typically a String representing the error message) if the data is invalid. This is a common point of confusion for developers used to standard Boolean logic where "true" means valid.

In this scenario, the helper method validatePostalCode returns aBoolean(true for valid, false for invalid). Because Guidewire expects a null result for success, a direct call to a Boolean method is insufficient.

Option A and Care incorrect because they evaluate to a Boolean value (true or false). If the method returns true, the validation engine receives true instead of null, which it incorrectly interprets as a validation failure.

Option Bis syntactically incorrect as it compares a Boolean to null.

Option Duses the ternary operator to map the Boolean result to the expected Guidewire logic. If validatePostalCode is true (valid), the expression returns null, which the system treats as "no error found." If the method is false (invalid), it returns a non-null value (in this exam wording, false). Since false is not null, the Guidewire validation engine identifies this as a failure and prevents the data from being committed or advancing to the next stage.

While best practices in a production environment suggest returning a descriptiveStringfor the user (e.g., "Invalid postal code for this country"), for the purposes of the developer exam, the logic focuses on theNull/Non-Nullrequirement. This mechanism ensures that developers understand how the Guidewire validation framework triggers errors based on the presence of a return value rather than a Boolean state.