🤖 Repeat tests. Repeat tests. Repeat tests.

Repeats tests using different inputs
(Data-Driven Testing):

- test runner independent: works with your current setup
- generates test titles that are descriptive, unique, for any
JavaScript type (not just JSON)
- loops over every possible combination of inputs
(cartesian product)
- can use random functions (fuzz testing)
- snapshot testing friendly

Example

``js
// The examples use Ava but any test runner works (Jest, Mocha, Jasmine, etc.)
import test from 'ava'

import multiply from './multiply.js'

import { each } from 'test-each'

// The code we are testing

// Repeat test using different inputs and expected outputs
each(
[
{ first: 2, second: 2, output: 4 },
{ first: 3, second: 3, output: 9 },
],
({ title }, { first, second, output }) => {
// Test titles will be:
// should multiply | {"first": 2, "second": 2, "output": 4}
// should multiply | {"first": 3, "second": 3, "output": 9}
test(should multiply | ${title}, (t) => {
t.is(multiply(first, second), output)
})
},
)

// Snapshot testing. The output is automatically set on the first run,
// then re-used in the next runs.
each(
[
{ first: 2, second: 2 },
{ first: 3, second: 3 },
],
({ title }, { first, second }) => {
test(should multiply outputs | ${title}, (t) => {
t.snapshot(multiply(first, second))
})
},
)

// Cartesian product.
// Run this test 4 times using every possible combination of inputs
each([0.5, 10], [2.5, 5], ({ title }, first, second) => {
test(should mix integers and floats | ${title}, (t) => {
t.is(typeof multiply(first, second), 'number')
})
})

// Fuzz testing. Run this test 1000 times using different numbers.
each(1000, Math.random, ({ title }, index, randomNumber) => {
test(should correctly multiply floats | ${title}, (t) => {
t.is(multiply(randomNumber, 1), randomNumber)
})
})
`

Install

`
npm install -D test-each
`

This package works in both Node.js >=18.18.0 and
browsers.

This is an ES module. It must be loaded using
an import or import() statement,
not require(). If TypeScript is used, it must be configured to
output ES modules,
not CommonJS.

Usage

`js
import { each } from 'test-each'

const inputs = [
['red', 'blue'],
[0, 5, 50],
]
each(...inputs, (info, color, number) => {})
`

Fires callback once for each possible combination of inputs.

Each input can be an array, a
function or an integer.

A common use case for callback is to define tests (using any test runner).

info is an object whose properties can be used to generate
test titles.

$3

Each combination of parameters is stringified as a title available in the
callback's first argument.

Titles should be included in test titles to make them descriptive and unique.

Long titles are truncated. An incrementing counter is appended to duplicates.

Any JavaScript type is
stringified,
not just JSON.

You can customize titles either by:

- defining title properties in inputs that are
plain objects
- using the info argument

`js
import { each } from 'test-each'

each([{ color: 'red' }, { color: 'blue' }], ({ title }, param) => {
// Test titles will be:
// should test color | {"color": "red"}
// should test color | {"color": "blue"}
test(should test color | ${title}, () => {})
})

// Plain objects can override this using a title property
each(
[
{ color: 'red', title: 'Red' },
{ color: 'blue', title: 'Blue' },
],
({ title }, param) => {
// Test titles will be:
// should test color | Red
// should test color | Blue
test(should test color | ${title}, () => {})
},
)

// The info argument can be used for dynamic titles
each([{ color: 'red' }, { color: 'blue' }], (info, param) => {
// Test titles will be:
// should test color | 0 red
// should test color | 1 blue
test(should test color | ${info.index} ${param.color}, () => {})
})
`

$3

If several inputs are specified, their
cartesian product is used.

`js
import { each } from 'test-each'

// Run callback five times: a -> b -> c -> d -> e
each(['a', 'b', 'c', 'd', 'e'], (info, param) => {})

// Run callback six times: a c -> a d -> a e -> b c -> b d -> b e
each(['a', 'b'], ['c', 'd', 'e'], (info, param, otherParam) => {})

// Nested arrays are not iterated.
// Run callback only twice: ['a', 'b'] -> ['c', 'd', 'e']
each(
[
['a', 'b'],
['c', 'd', 'e'],
],
(info, param) => {},
)
`

$3

If a function is used instead of an array, each iteration fires it and uses
its return value instead. The function is called with the
same arguments
as the callback.

The generated values are included in test titles.

`js
import { each } from 'test-each'

// Run callback with a different random number each time
each(['red', 'green', 'blue'], Math.random, (info, color, randomNumber) => {})

// Input functions are called with the same arguments as the callback
each(
['02', '15', '30'],
['January', 'February', 'March'],
['1980', '1981'],
(info, day, month, year) => ${day}/${month}/${year},
(info, day, month, year, date) => {},
)
`

$3

Integers can be used instead of arrays to multiply the number of iterations.

This enables fuzz testing when combined
with input functions and libraries like
faker.js,
chance.js or
json-schema-faker.

`js
import faker from 'faker'

// Run callback 1000 times with a random UUID and color each time
each(
1000,
faker.random.uuid,
faker.random.arrayElement(['green', 'red', 'blue']),
(info, randomUuid, randomColor) => {},
)

// info.index can be used as a seed for reproducible randomness.
// The following series of 1000 UUIDs will remain the same across executions.
each(
1000,
({ index }) => faker.seed(index) && faker.random.uuid(),
(info, randomUuid) => {},
)
`

$3

This library works well with
snapshot testing.

Any library can be used
(snap-shot-it,
Ava snapshots,
Jest snapshots,
Node TAP snapshots, etc.).

`js
import { each } from 'test-each'

// The output is automatically set on the first run,
// then re-used in the next runs.
each(
[
{ first: 2, second: 2 },
{ first: 3, second: 3 },
],
({ title }, { first, second }) => {
test(should multiply outputs | ${title}, (t) => {
t.snapshot(multiply(first, second))
})
},
)
`

$3

If callback's parameters are directly modified, they should be
copied to prevent side effects for the next iterations.

`js
import { each } from 'test-each'

each(
['green', 'red', 'blue'],
[{ active: true }, { active: false }],
(info, color, param) => {
// This should not be done, as the objects are re-used in several iterations
param.active = false

// But this is safe since it's a copy
const newParam = { ...param }
newParam.active = false
},
)
`

$3

iterable() can be used to iterate over each combination
instead of providing a callback.

`js
import { iterable } from 'test-each'

const combinations = iterable(
['green', 'red', 'blue'],
[{ active: true }, { active: false }],
)

for (const [{ title }, color, param] of combinations) {
test(should test color | ${title}, () => {})
}
`

The return value is an
Iterable.
This can be converted to an array with the spread operator.

`js
const array = [...combinations]

array.forEach(([{ title }, color, param]) => {
test(should test color | ${title}, () => {})
})
`

API

each(...inputs, callback)

inputs: Array | function | integer (one or several)\
callback: (info, ...params) => void

Fires callback with each combination of params.

iterable(...inputs)

inputs: Array | function | integer (one or several)\
_Return value_:
[Iterable<[info, ...params]>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators#Iterables)

Returns an
Iterable
looping through each combination of params.

$3

_Type_: object

#### info.title

_Type_: string

Like params but stringified. Should be used in
test titles.

#### info.titles

_Type_: string[]

Like info.title but for each param.

#### info.index

_Type_: integer

Incremented on each iteration. Starts at 0.

#### info.indexes

_Type_: integer[]

Index of each params inside each initial
input.

$3

_Type_: any (one or several)

Combination of inputs for the current iteration.

Support

For any question, _don't hesitate_ to submit an issue on GitHub.

Everyone is welcome regardless of personal background. We enforce a
Code of conduct in order to promote a positive and
inclusive environment.

Contributing

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sharing it online.

If the documentation is unclear or has a typo, please click on the page's Edit`
button (pencil icon) and suggest a correction.

If you would like to help us fix a bug or add a new feature, please check our
guidelines. Pull requests are welcome!