test VS tlaplus

The de-facto standard for testing an Elm application is elm-test. However, as noted in the README:

Once all that handwritten C code was solid, I needed to make sure the C generated from Elm was working properly. I found the source for the core library's unit tests and decided to port them into my project and add some of my own tests. You can run the tests in WebAssembly in your browser too. (Funnily enough, one of the biggest challenges was getting the Elm Test framework itself to run! The framework is more complex than the tests themselves. I still need to come back to the fuzzer tests!)

Lesson Learned: Elm has built in recursion improvements for a variety of positive reasons, and you should think in recursion to solve looping problems. Use property/fuzz tests and bounds checking with early exit to prevent this from locking up your UI (i.e if > 9000, omg abort). If you’re algorithm is reasonable, but the data set is just gigantic, offload to a server instead for more horsepower. Or Workers if you don’t have server chops, can’t upload the large data, or don’t trust your server devs. (“But Doc, I’m the server dev!” Good joke. Ever̸y̴b̸ody laugh. Roll on s̵͓̆nâ̶̱re drum. Curtains.)

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https://github.com/tlaplus/tlaplus/blob/master/tlatools/org....

In any case, our whole team thinks TLA is great, and we're happy people like you and Ron find it so useful and insightful. We also think it is a very insightful.

There are no tests! There are various ways to test concurrent data structures. You could use a stress test, where you spawn a lot of threads and let them mutate the map in a random way and then check the consistency of the map and some invariants. You could learn TLA+ and write a formal model of the map and then verify it.

Dafny and Whiley are two examples with explicit verification support. Idris and other dependently typed languages should all be rich enough to express the required predicate but might not necessarily be able to accept a reasonable implementation as proof. Isabelle, Lean, Coq, and other theorem provers definitely can express the capability but aren't going to churn out much in the way of executable programs; they're more useful to guide an implementation in a more practical functional language but then the proof is separated from the implementation, and you could also use tools like TLA+.

https://dafny.org/

https://whiley.org/

https://www.idris-lang.org/

https://isabelle.in.tum.de/

https://leanprover.github.io/

https://coq.inria.fr/

http://lamport.azurewebsites.net/tla/tla.html

I wish something like Lamport's TLA+ (https://lamport.azurewebsites.net/tla/tla.html) was supported in modern language compilers - perhaps with annotations/macros and a mini formal DSL.

Checking the invariant with assert is also useful in my limited experience with concurrency.

https://lamport.azurewebsites.net/tla/tla.html

One advantage of formal methods is in determining "what was expected" (including all the goofy edge cases) without having to burrow into the details of code.

Take a look at Alloy (http://alloytools.org/) and TLA+ (https://lamport.azurewebsites.net/tla/tla.html) for example. (Or even the ancient Z ("Zed") notation (https://www.cs.cmu.edu/~15819/zedbook.pdf)).

The pcal generator does *not* generate a definition for the set of labels. However, some users have suggested to add such a feature: https://github.com/tlaplus/tlaplus/issues/613