In the WCF project, the file App_Code\CustomUserNameValidator.cs contains simple implementations of validators for Username/Password and Certificates. By default, these validators only check for null values.
When you test your presentation project during development (using the TestBinding), these validators are not called. The validators are used when testing the deployed application (using the ReleaseBinding).
If you want to implement custom validation, you can edit the code. For more information, see the following MSDN reference topics:
How to: Use a Custom User Name and Password Validator: https://msdn.microsoft.com/en-us/library/aa702565(v=vs.110).aspx
How to: Create a Service that Employs a Custom Certificate Validator: https://msdn.microsoft.com/en-us/library/ms733806(v=vs.110).aspx