proptest
v0.0.4
Published
Property based testing for TypeScript
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Property-based testing for TypeScript and JavaScript
This is an implementation of property-based testing a'la QuickCheck for TypeScript. It works with plain JavaScript and languages like CoffeeScript too.
Shrinking is done by generating lazy rose trees of values directly. This means that you can map and chain generators and get correct shrinking functions "for free". This is a deviation from the original Haskell library but works well in languages without typeclasses. (The same approach is taken in other implementations such as Hedgehog for Haskell, Hypothesis for Python and test.check for Clojure)
Usage with mocha and jest
import * as QC from 'proptest'
const property = QC.createProperty(it)
describe('f', () => {
property(
'is commutative',
QC.nat.two(),
([x, y]) => (expect(f(x, y)).toEqual(f(y, x)), true)
)
})
(to be improved; remove returning a boolean: discussion)
Usage with tape
import * as QC from 'proptest'
const check = QC.adaptTape(test)
check('f commutative', QC.nat.two(), ([x, y]) => f(x, y) === f(y, x))
Usage with AVA
import * as QC from 'proptest'
test('f commutative', t => {
t.true(QC.stdoutForall(QC.nat.two(), ([x, y]) => f(x, y) === f(y, x)))
})
(to be improved, also see ava#1692)
Usage without a library as an assertion
import * as QC from 'proptest'
QC.assertForall(QC.nat.two(), ([x, y]) => f(x, y) === f(y, x))
The API exports a function search
which return returns {'ok': true}
if the property
passed or {'ok': false}
and the counterexample (or other information) if it did not.
Installation
You can grab it from npm:
npm i -D proptest
You may use yarn:
yarn add --dev proptest
Contributors
- Simon Friis Vindum @paldepind (commits)
Ongoing discussions
License
MIT