Yes special characters, blank space ,numbers all these are 
independent entries user are suppose to insert into the 
application.so we need seperate test cases for each.

Thanks Deepanjan

It depends on the project/methodology in the process of 
your application. ie., In most of the Service Oriented 
applications, normally a document called "Rules matrix" 
will be provided by the Business Analysts, which talks 
about each field's data,length, category..etc. In such a 
case its not mandatory to write seperate testcases for 
these data validations, a tester can track/Monitor all such 
testing data, there itself in the Rules matrix.


Thus its depends on the methodology/Process of your project.