jsverify
proposal-pattern-matching
jsverify | proposal-pattern-matching | |
---|---|---|
5 | 67 | |
1,666 | 5,344 | |
0.1% | 0.9% | |
1.8 | 9.0 | |
about 3 years ago | 13 days ago | |
JavaScript | HTML | |
MIT License | MIT License |
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
jsverify
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The 5 principles of Unit Testing
Libraries like JSVerify or Fast-Check offer essential tools to facilitate property-based testing.
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Ask HN: What's your favorite software testing framework and why?
I tend to use anything that offers property-testing, since tests are much shorter to write and uncover lots more hidden assumptions.
My go-to choices per language are:
- Python: Hypothesis https://hypothesis.readthedocs.io/en/latest (also compatible with PyTest)
- Scala: ScalaCheck https://scalacheck.org (also compatible with ScalaTest)
- Javascript/Typescript: JSVerify https://jsverify.github.io
- Haskell: LazySmallCheck2012 https://github.com/UoYCS-plasma/LazySmallCheck2012/blob/mast...
- When I wrote PHP (over a decade ago) there was no decent property-based test framework, so I cobbled one together https://github.com/Warbo/php-easycheck
All of the above use the same basic setup: tests can make universally-quantified statements (e.g. "for all (x: Int), foo(x) == foo(foo(x))"), then the framework checks that statement for a bunch of different inputs.
Most property-checking frameworks generate data randomly (with more or less sophistication). The Haskell ecosystem is more interesting:
- QuickCheck was one of the first property-testing frameworks, using random genrators.
- SmallCheck came later, which enumerates data instead (e.g. testing a Float might use 0, 1, -1, 2, -2, 0.5, -0.5, etc.). That's cute, but QuickCheck tends to exercise more code paths with each input.
- LazySmallCheck builds up test data on-demand, using Haskell's pervasive laziness. Tests are run with an error as input: if they pass, we're done; if they fail, we're done; if they trigger the error, they're run again with slightly more-defined inputs. For example, if the input is supposed to be a list, we try again with the two forms of list: empty and "cons" (the arguments to cons are both errors, to begin with). This exercises even more code paths for each input.
- LazySmallCheck2012 is a more versatile "update" to LazySmallCheck; in particular, it's able to generate functions.
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Property Based Testing Framework for Node
The usage of hypothesis is very intuitive and simple, and presents the concept of property-based testing perfectly. So I also wanted to find an equivalent alternative in Node. Two of them have high star ratings on Github, JSVerify with 1.6K stars and fast-check with 2.8K stars. So I took some time to study fast-check a little bit and try to get closer to my daily work.
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Machine Readable Specifications at Scale
Systems I've used for this include https://agda.readthedocs.io/en/v2.6.0.1/getting-started/what... https://coq.inria.fr https://www.idris-lang.org and https://isabelle.in.tum.de
An easier alternative is to try disproving the statement, by executing it on thousands of examples and seeing if any fail. That gives us less confidence than a full proof, but can still be better than traditional "there exists" tests. This is called property checking or property-based testing. Systems I've used for this include https://hypothesis.works https://hackage.haskell.org/package/QuickCheck https://scalacheck.org and https://jsverify.github.io
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React to Elm Migration Guide
Using create-react-app, you’ll run npm test which uses Jest internally. If you are dealing with a lot of data on the UI, or using TypeScript, use JSVerify for property tests. For end to end tests, Cypress is a great choice.
proposal-pattern-matching
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Coming to grips with JS: a Rubyist's deep dive
Note, however, that there is a proposal to add pattern matching to JS.
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Level up your Typescript game, functionally - Part 2
There's an ECMAScript proposal that is in the works to add this feature to the language! It's going to look something like this.
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Building React Components Using Unions in TypeScript
More importantly, TypeScript typically commits to build things into itself when the proposal in JavaScript reaches Stage 3. The pattern matching proposal in JavaScript is Stage 1, but depends on many other proposals as well that may or may not need to be at Stage 3 as well for it to work. This particular proposal is interested on pattern matching on JavaScript Objects and other primitives, just like Python does with it’s native primitives. These are also dynamic types which helps in some areas, but makes it harder than others. Additionally, the JavaScript type annotations proposal needs to possibly account for this. So it’s going to be awhile. Like many years.
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Explicit Software Design. Preliminary Conclusions
For true™ functional programming in JS, native pattern matching and partial function application are missing (at least for now: 1, 2). For proper OOP, it lacks real interfaces and compile-time dependency injection.
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TypeScript Is Surprisingly OK for Compilers
The proposal for pattern matching syntax seems more akin to what they're looking for.
https://github.com/tc39/proposal-pattern-matching
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[AskJS] C# in every Node.js job posting?
There's a proposal to add something like that to JavaScript but it's been stuck in limbo since 2017 although there are libraries like ts-pattern which implement it already.
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[AskTS] What do you think will be the future of runtime type checking?
I'll admit, it is easy to assert that the TypeScript language should not be involved in the matters of packages but I also wonder if we're moving towards a point where interfaces will be as common as namespaces and whether or not it would be sensible for the language to incorporate such type assertions into the language formally, after all, it already compiles to various forms of JavaScript and there is a stage 1 proposal submitted to the TC39 committee to give JavaScript pattern matching. If adopted, wouldn't it make sense to allow TypeScript to compile a type into a type guard for the native JavaScript pattern matcher?
- Updates from the 96th TC39 meeting
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Mostly adequate guide to FP (in JavaScript)
Both are active tc39 proposals :)
https://github.com/tc39/proposal-pipeline-operator - Stage 2
https://github.com/tc39/proposal-pattern-matching - Stage 1
Hopefully we get both in the next couple of years.
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CoffeeScript for TypeScript
We often add promising TC39 proposals into Civet so people can experiment without waiting.
We've added https://github.com/tc39/proposal-pipeline-operator, a variant of https://github.com/tc39/proposal-pattern-matching, a variant of https://github.com/tc39/proposal-string-dedent and others.
Since our goal is to be 99% compatible with ES we'll need to accommodate any proposals that become standard and pick up anything TC39 leaves on the table (rest parameters in any position, etc.)
What are some alternatives?
greenlight - Clojure integration testing framework
fp-ts - Functional programming in TypeScript
testy - test helpers for more meaningful, readable, and fluent tests
package.elm-lang.org - website for browsing packages and exploring documentation
LazySmallCheck2012 - Lazy SmallCheck with functional values and existentials!
content - The content behind MDN Web Docs
fast-check - Property based testing framework for JavaScript (like QuickCheck) written in TypeScript
ecma262 - Status, process, and documents for ECMA-262
hitchstory - Type-safe YAML integration tests. Tests that write your docs. Tests that rewrite themselves.
proposal-pipeline-operator - A proposal for adding a useful pipe operator to JavaScript.
datadriven - Data-Driven Testing for Go
proposal-record-tuple - ECMAScript proposal for the Record and Tuple value types. | Stage 2: it will change!