Derive Clone for App

[0xForerunner]

This is useful in testing. It's common to run a complicated setup procedure to build an app state, then to run different tests on that app. Rather that constantly rebuilding the state this allows you to clone it around.

It seems that perhaps other useful derives are missing as well (Debug being an obvious one). Though I don't immediately have a use case for that.

[DariuszDepta]

Hi @ewoolsey!, just to make things clearer, could you provide an example of such test suite where the app is cloned and then used in multiple tests?

[DariuszDepta]

@ewoolsey I am closing this PR as no answer received. This PR can be reopened in the future if there will be a reason to add requested derives to App.

Remark/workaround:
In tests we do, when there is a need to do complicated App setup to be used in multiple tests, we implement utility function that does this setup and returns the App. This function is called in each test, so each test has fresh copy of the App. This is an equivalent of cloning the App without a risk of interference between tests, like setup-ing App, running one test that possibly changes the App state, then cloning the App and using it in another test with the state that is not initial anymore.

I hope this helps.

[0xForerunner]

@ewoolsey I am closing this PR as no answer received. This PR can be reopened in the future if there will be a reason to add requested derives to App.

Remark/workaround: In tests we do, when there is a need to do complicated App setup to be used in multiple tests, we implement utility function that does this setup and returns the App. This function is called in each test, so each test has fresh copy of the App. This is an equivalent of cloning the App without a risk of interference between tests, like setup-ing App, running one test that possibly changes the App state, then cloning the App and using it in another test with the state that is not initial anymore.

I hope this helps.

Hey sorry for missing the reply my apologies. Yes your workaround is what I'm currently doing. This is very computationally expensive when performing 10 thousand randomized tests. Being able to clone this structure would be ideal. As far as I'm aware there are exactly no down sides to deriving Clone so my question to you would be, why not?

[0xForerunner]

For more context, I have very complicated setup procedure for my app, around 500 lines or so. This base state is then modified using an rng to test edge cases. Running my 500 line setup procedure 10000 times in incredible slow.

[DariuszDepta]

@ewoolsey Just let me know if using Clone is the performance better in your case. Thanks.

[0xForerunner]

@ewoolsey Just let me know if using Clone is the performance better in your case. Thanks.

Just did a quick benchmark and one of my fuzz tests had a 5x perf improvement :) Thanks for approving the PR. Really appreciate it!