turn testExec into a wandtesting package
use a type cache
test:
- nil return values
- options in variadic
- options in pointer
- options in slice
- options in slice and pointer
- parameters in pointers
- parameters in slices
- parameters in slices and pointers
- implementation in pointer
- implementation in slice => not accepted
- implementation in pointer and slice => not accepted
- plurality
- env parsing
- plurality in input validation
