ava-check
adds the generative testing power of testcheck-js
to AVA. This allows some of your AVA tests
to accept arguments and ensure your tests pass not just under your contrived
test cases but also pass for hundreds of randomly generated test cases.
Install ava-check
using yarn.
yarn add --dev ava-check
Or using npm
npm install --save-dev ava-check
Then include ava-check
in your test.
const { check, gen } = require('ava-check')
const test = require('ava')
const { check, gen } = require('ava-check')
test('addition is commutative', check(gen.int, gen.int, (t, numA, numB) => {
t.true(numA + numB === numB + numA)
}));
The gen
object is provided directly by testcheck
and defines what type of
values to generate. The test will be run numerous times with randomly generated
values, ensuring all expectations are met for every run. If a test expectation
fails, then the test will re-run with "smaller" values until the smallest
failing value is found which can better help explain edge cases with your test
and produce consistent results, despite being initially fueled by randomness.
For example, here's a test which we expect would fail:
const test = require('ava')
const { check, gen } = require('ava-check')
test('division is commutative', check(gen.sPosInt, gen.sPosInt, (t, numA, numB) => {
t.true(numA / numB === numB / numA)
}));
When we run this test, we find the smallest failing test:
> ava test
1 failed
division is commutative ( 1, 2 )
t.true(numA / numB === numB / numA)
| | | |
1 2 2 1
If a test is taking a long time, needs to generate larger values, or should be
run with a consistent random seed, you can alter the behavior with options
:
{
times: number; // the number of test cases to run. Default: 100
maxSize: number; // the maximum "size" of the test data. Default: 200
seed: number; // defaults to a random value from 1 to 2^32-1.
}
To use these options with your check, include an options object before the argument generators.
test('runs 10 times', check({ times: 10 }, gen.posInt, (t, n) => {
t.true(x >= 0)
}))
To learn more about property testing, or to learn about the available value
generators, check out testcheck
.