junit-quickcheck VS ddtj

For anyone interested, there's also https://github.com/pholser/junit-quickcheck . Haven't used it myself but looks like an interesting library to explore. It's based on QuickCheck as well AFAIK.

Thank you for the insightful reply. I did struggle to convert the original algorithm I wrote (with while loops / continue / break) to a more functional style using unfold, and also faced an issue with the type signatures when I tried to break down the contents of Stream.unfoldRight to multiple functions, which is reflected to the messy state you mentioned. Regarding property based testing, I used junit-quickcheck and the "symmetry" property check was one I meant to write but wasn't quite sure how to create a generator for it. I created an issue to track my attempt to incorporate your suggestions in case you are interested in following this. Thanks again!

A quick Google search shows that java has a library for this (here) but I've never used it in java so can't attest to it.

QuickcCheck-type tools (generators for tests that know about the edge cases of a domain - e. g. for the domain of numbers considering things like 0, the infinities, various almost-and-just-over powers of two, NaN and mantissas for floats, etc.):

* QuickCheck: https://hackage.haskell.org/package/QuickCheck

* Hypothesis: https://hypothesis.readthedocs.io/en/latest/

* JUnit QuickCheck: https://github.com/pholser/junit-quickcheck

Fuzz testing tools (tools which mutate the inputs to a program in order to find interesting / failing states in that program). Generally paired with code coverage:

* American Fuzzy Lop (AFL): https://github.com/google/AFL

* JQF: https://github.com/rohanpadhye/JQF

Mutation / Fault based test tools (review your existing unit coverage and try to introduce changes to your _production_ code that none of your tests catch)

* PITest: https://pitest.org/

If you want an easy way to have better mutation coverage, check out property based testing. Eg junit-quickcheck for Java.

https://github.com/pholser/junit-quickcheck

Very cool. I started working on something similar but never got very far with it. Too busy with other things. I also felt the performance was too problematic. I was also "too eager" to mock which is bad. If you get it right I think it can be huge. Good luck!

I suggest watching the ddtj project to see when it gets updated with a new PR. You can also follow me on twitter to keep up to date with the latest developments. I have some great ideas for the core technology of DDT that go well beyond testing alone. There’s a lot of untapped potential here that we need to explore.

But I’m running a bit ahead. Let’s talk about what’s happening with the code right now… Or at least in the current PR that’s still waiting for more test coverage.

With that I merged two PRs. This monster PR finally implements all the debugging logic so we can collect all the data we need. Then I merged a small fix which gave the performance boost I’ll discuss shortly.

Last week I spent 5 days building and designing the DDTJ project. Hopefully, I’ll complete the MVP by this weekend. As we left the series last week, I was stuck. This week there’s a bit of an improvement…

We almost have an open source project. Well, technically we already have the source code and a few lines of code, but it still isn't exactly a "project". Not in the sense of "it needs to do something useful". But it compiles, runs unit tests and even has 80% code coverage. That last one was painful. I'm not a fan of arbitrary metrics to qualify the quality of code. The 80% code coverage is a good example of this. Case in point, this code. Currently, the source code looks like this:

I finished the first draft of the developer guide for DDTJ today. You can check it out here.