How to write a test case for the agreement window which comes at the time of installation?
Without knowing more, I think the general framework is....
Step 1, list your requirements.
Step 2, list requirements that are inferred by your requirements.
Step 3, come up with scenarios that exercise the set of requirements derived from steps 1 and 2.
Step 4, create permutations of scenarios and environmental factors.
Luckily, Your agreement can be treated as a requirement document for you.
You can created test cases based on the agreement conditions. Also you want to check the test for
1. System requirement mismatch
3. Cancellation and re-installation
4. Installation and installation
5. installation on already installed
6. two installation same time.
and so on...