Add a formal description of cartesian-product-switch.
For the existing usage example, show the somewhat convoluted code one would have to write by hand otherwise. In fact there are 2 straightforward alternatives and point out choosing and converting between those 2 is much harder than in the case of the cartesian-product-switch equivalents.
Add more cartesian-product-switch usage examples.
Add a formal description of all built-in testclause kinds.
Explain how cartesian-product-switch makes it easier to ensure you've considered all possible case combinations.