On some occassions you might do well with just giving instructions in one test case step / test description. This works if you can be sure that the tester will be able to work effectively with general description. Your example is an easy one for human, so basically you can be quite sure that tester will be able to test the right things with quite roughly detailed test case.
For more general approach, that works also on the fields where the tester does not yet know the system under test thoroughly and needs more instructions on what to test you can use test requirements.
1) Split your requirements in things that you want to test about the requirements. In your example you could make one requirement giving instructions what you should test about text fields and another about what you should test about numerical fields.
2) Link these test requirements to your test cases. As test case steps you can just list the things the tester needs to go trough ( the contact for fields ) - he will have the further instructions in the test requirement.
If you later change the specification, for example if you would add arabic support for your text fields and would need to test that you would just need to change the test requirement.