Test Cases are the reusable units. Test Cases can be referenced in other Test Cases to create modularly built tests.
Being able to reuse Test Cases means that you should put some thought into how to design them so that they are as specific as they need to be while also being generic enough to reuse in different situations.
You can improve the flexibility of a Test Case by:
Using references (Section 3.14.3, “Using references for data in Test Cases”) instead of concrete data if the data can change. References allow you to feed a Test Case with different data each time you reuse it.
Using the abstract components (e.g. component with text, component with text input, graphics component) (Section 6.8.2, “Abstract, concrete and toolkit specific components”) to specify your tests wherever possible.
Allowing the component it tests to be defined when you reuse it (Section 3.15.3, “Entering and reassigning component names in the Component Names View”).