The parameters of an action are bifurcated into mandatory and nonThere are two types of parameters; Mandatory and Non-mandatory.

For Nonnon-Mandatory mandatory parameters, empty (" "/$NULL$) data is accepted as a data. The action on receiving empty data, accordingly uses the default data for the parameter, however, for the string parameter, it will continue using the empty (zero length string).

For Mandatory parameters, empty (" "/$NULL$) data is not accepted as a data and you would will need to enter valid data accordingly.
Custom Actions can have parameters set to mandatory/non-mandatory as per requirement.based on the requirement.

See also,

• Creating a Test Case
• Updating Test Data
• Editing a Test Case
• Searching a Test Case
• Removing a Test Case
• Sync Test Case
• Empty Data Handling
• Critical Data Protection