Create a Form with a text field and mark it as required. A validation should happen and you shouldn't be able to submit forms with empty text value.
1) Go to Site Admin > Forms
2) Create a new Form with Text Field and mark it as required.
3) Instantiate the Form portlet to a page
4) Select the created form on step 2.
Expected Result: Users shouldn't be able to submit a form unless they specify a value for the text field.