Workflow VS skiplistrs

I was part of that debate, I remember a rather interesting point of discussion: Is the main operation "apply" or "dedup"

Apply seems to be the common notion of event sourcing: There is a function apply that takes a state an event and yields a new state. Then, starting in an init state and iteratively applying the entire event history, boom, latest state restored.

Dedup has a lot of charm though: Run and rerun your code, if that step of your code is executed for the first time (no corresponding event in the event history) execute the step and store its result as an event in the history, however, if that step of your code is executed for the second, third time (there is a corresponding event in the event history) do not execute the step and return its result from the event in the history. The Haskell Workflow Package (https://hackage.haskell.org/package/Workflow) is a good example

Temporal follows the second approach, so "proper" Event Sourcing? You be the judge :)

Sure - here's a simple fuzzer from a rope (fancy string) library I wrote a few years ago back when I was still learning rust. (Don't judge me!):

https://github.com/josephg/skiplistrs/blob/master/tests/test...

In a loop it simply randomly decides whether to insert, delete or replace some text, and after any action checks that the state is valid (In this case via a call to check2()).

You can go way deeper with this sort of thing if you want, with more complex models, random item generation and simplifiers to help pare down problems to simple test cases. And you can have more complex state - for example, where you also track interaction between multiple items. For example, if your state is a few users, and you also track one user paying another user and verify the total balance across all users is unchanged.

But you don't need to go deep for fuzz testing to be worthwhile. Even something as simple as this little loop is a remarkably effective bug finder.