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https://github.com/nicolast/hedgehog-stateful-demo

A demonstration of stateful systems testing using Hedgehog
https://github.com/nicolast/hedgehog-stateful-demo

haskell haskell-learning hedgehog property-based-testing property-testing quickcheck state-machine state-machine-testing testing

Last synced: 27 days ago
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A demonstration of stateful systems testing using Hedgehog

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README 

        
# hedgehog-stateful-demo



This repository contains some code demonstrating testing of a stateful,

database-backed application using [Hedgehog][hedgehog], a library

similar in spirit to the well-known [QuickCheck][quickcheck] library.

Hedgehog comes with

[built-in functionality to test state machines][hedgehog-fsm] but the

API may be a slightly daunting, hence this demo.



It's based on a blog-post by [Jacob Stanley][jacob-stanley]:

"[How to use Hedgehog to test a real world, large scale, stateful app][blog]".

Make sure to read it first!



## Importing the Original Code

[The first commit][a7f2e4b32f4] imports all code from the original blog-post up

to the **Generate commands** section.



[The second commit][8a7fefdab86] adds the code from the **Generate commands**

and **Execute commands** sections.



[The third commit][48ec8df136e] adds code from the **Delete some users**

section, which causes the tests to fail, as expected and explained in the

original article.



[The fourth commit][7341460c0e7] applies the changes from the

**Fix the model** section, which causes the tests to succeed again.



[The fifth commit][4489784f61e] adds test-case labelling, as explained in the

**Check commands get used** section of the original article.



[The sixth commit][c76306356e2] adds business rule validation, which causes the

tests to fail again, as expected. See the **Assert business rules** section in

the original article.



[The seventh commit][956dd5d59f7] reverts the previous one, since we don't want

failing tests. Hence, the code is back to that of the

**Check commands get used** section of the original article.



## Reworking using Hedgehog State-Machine Testing

The above tests are re-implemented using the Hedgehog State-Machine testing

functionality in similar commits:



- The **Generate commands** and **Execute commands** functionality originally

  implemented in [here][8a7fefdab86] is [here][a7f2e-130aef]

  ([compare][8a7fe-130ae]). Note these changes require a slight modification of

  the `abort` function, which clutters the diff somewhat.



- The **Delete some user** functionality originally implemented

  [here][48ec8df136e] is [here][130aef-5a539] ([compare][48ec8-5a539]).



- The fixes from the **Fix the model** section originally implemented

  [here][7341460c0e7] is [here][5a539-b9f906] ([compare][73414-b9f90]).



- The code changes to label test-cases from the **Check commands get used**

  section originally implemented [here][4489784f61e] is [here][b9f906-e6a5e]

  ([compare][44897-e6a5e]).



[The final diff][a7f2e-e6a5e] resembles [the original one][a7f2e-956dd] quite

well!



## Making Cabal Happy

[This commit][cbd68a8c786] makes the changes required for `cabal test` to

succeed.



[hedgehog]: https://hedgehog.qa/

[quickcheck]: https://hackage.haskell.org/package/QuickCheck

[hedgehog-fsm]: https://hackage.haskell.org/package/hedgehog-1.2/docs/Hedgehog.html#g:5

[jacob-stanley]: https://jacobstanley.io

[blog]: https://jacobstanley.io/how-to-use-hedgehog-to-test-a-real-world-large-scale-stateful-app/



[a7f2e4b32f4]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/a7f2e4b32f4fb1ad6ecb46537c5752b734a8156e

[8a7fefdab86]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/8a7fefdab86635915402b1bada48d99b61c04aab

[48ec8df136e]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/48ec8df136e3f54c9a82bb0f39aa42cd55c6cf3f

[7341460c0e7]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/7341460c0e7cbf8681b68fe9ca893d3ea6e95d91

[4489784f61e]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/4489784f61e2956992ee4dcdb7b194387c33e1a2

[c76306356e2]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/c76306356e2a54a8a493478e1a710753ba51fd41

[956dd5d59f7]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/956dd5d59f7887f3562f9741e3a87b19c9d4f37b

[cbd68a8c786]: https://github.com/NicolasT/hedgehog-stateful-demo/commit/cbd68a8c786a5a17278e0ed63390aefa25d9b1e3



[a7f2e-130aef]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/a7f2e4b32f4fb1ad6ecb46537c5752b734a8156e...130aef61081f8eb430faca609b5fd9f7731eb821

[130aef-5a539]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/130aef61081f8eb430faca609b5fd9f7731eb821...5a5395a25f99f9ce177bbcf950f653528885e6ee

[5a539-b9f906]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/5a5395a25f99f9ce177bbcf950f653528885e6ee...b9f90643df745cccb6e12587b0fe94609cb5ca2d

[b9f906-e6a5e]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/b9f90643df745cccb6e12587b0fe94609cb5ca2d...e6a5e95e18cd23ce982bea7c6ca1e6126b47a5b3



[8a7fe-130ae]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/8a7fefdab86635915402b1bada48d99b61c04aab...130aef61081f8eb430faca609b5fd9f7731eb821

[48ec8-5a539]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/48ec8df136e3f54c9a82bb0f39aa42cd55c6cf3f...5a5395a25f99f9ce177bbcf950f653528885e6ee

[73414-b9f90]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/7341460c0e7cbf8681b68fe9ca893d3ea6e95d91...b9f90643df745cccb6e12587b0fe94609cb5ca2d

[44897-e6a5e]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/4489784f61e2956992ee4dcdb7b194387c33e1a2...e6a5e95e18cd23ce982bea7c6ca1e6126b47a5b3



[a7f2e-e6a5e]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/a7f2e4b32f4fb1ad6ecb46537c5752b734a8156e...e6a5e95e18cd23ce982bea7c6ca1e6126b47a5b3

[a7f2e-956dd]: https://github.com/NicolasT/hedgehog-stateful-demo/compare/a7f2e4b32f4fb1ad6ecb46537c5752b734a8156e...956dd5d59f7887f3562f9741e3a87b19c9d4f37b