Partial output validator from spec

[lungsin]

When writing spec, sometimes a test case is written with a certain property to lead for a certain output. For example, for a particular case, the input is designed such that the output is "yes". This additional information from the spec can be useful if it can be validated when the runner generates the tc; it would lead to a higher confidence that the solution produces a correct output when the validation passes, and early indication that at least one of the solution or the spec is buggy when the validation fails.

I'm not sure what API design that works well since it's possible that the test case consists of a bunch of queries and only some of these queries have certain properties.