cypress-each

A demo of mocha-each and custom describe.each and it.each implementation for Cypress

🎓 Study the course Cypress Plugins

• Lesson f9: Test the data edge cases by making API calls
• Lesson f10: Run the same test in different resolutions
• Lesson f11: Split the data-driven tests across several spec files
• Lesson f12: Store viewports in a JSON file or config
• Lesson f13: Create tests from fetched data
• Lesson f14: Create N predetermined tests
• Lesson f15: Test multiple pages

Blog posts

• Dynamic API Tests Using Cypress-Each Plugin
• Refactor Tests To Be Independent And Fast Using Cypress-Each Plugin
• Test your sitemap using Cypress

Videos

• Using cypress-each To Create Separate Tests
• Test Each URL From Sitemap In Its Own Separate Cypress Test
• Using Faker to generate test data and execute separate tests using cypress-each plugin

Install and use

# install using NPM
$ npm i -D cypress-each
# install using Yarn
# yarn add -D cypress-each

Import cypress-each in a single spec or in Cypress support file

import 'cypress-each'
// now can use describe.each and it.each

Let's create a separate test for each selector from a list

import 'cypress-each'

// create a separate test for each selector
const selectors = ['header', 'footer', '.new-todo']
it.each(selectors)('element %s is visible', (selector) => {
  cy.visit('/')
  cy.get(selector).should('be.visible')
})
// creates tests
// "element header is visible"
// "element footer is visible"
// "element .new-todo is visible"

item index

In addition to the item, the callback receives the index

it.each(selectors)('element %s is visible', (selector, k) => {
  // k is 0, 1, 2, ...
})

Multiple arguments

You can pass multiple arguments into the callback function by using an array of arrays. For example, to check if an element is visible, invisible, or exists, you can have both a selector and the assertion string for each item.

const data = [
  // each entry is an array [selector, assertion]
  ['header', 'be.visible'],
  ['footer', 'exist'],
  ['.new-todo', 'not.be.visible'],
]
it.each(data)('element %s should %s', (selector, assertion) => {
  cy.visit('/')
  cy.get(selector).should(assertion)
})
// creates tests
// "element header should be.visible"
// "element footer should exist"
// "element .new-todo should not.be.visible"

Repeat the test N times

You can use this module to simply repeat the test N times

// repeat the same test 5 times
it.each(5)('test %K of 5', function (k) {
  // note the iteration index k is passed to each test
  expect(k).to.be.within(0, 4)
})

// you can repeat the suite of tests
describe.each(3)('suite %K of 3', function (k) {
  ...
})

See the repeat-spec.js

Test and suite titles

You can use the arguments to the test callback in the test title in order.

it.each([10, 20, 30])('number is %d', (x) => { ... })
// creates the tests
// "number is 10"
// "number is 20"
// "number is 30"

You can also insert the arguments from the test callback via positions (0-based) into the title

const list = [
  ['foo', 'main'],
  ['bar', 'edge'],
]
it.each(list)('testing %1 value %0')
// "testing main value foo"
// "testing edge value bar"

If you want to use the iteration variable in the title, use %k for zero-based index, or %K for one-based index.

it.each([10, 20, 30])('checking item %k', (x) => { ... })
// creates the tests
// "checking item 0"
// "checking item 1"
// "checking item 2"
it.each([10, 20, 30])('checking item %K', (x) => { ... })
// creates the tests
// "checking item 1"
// "checking item 2"
// "checking item 3"

You can use %N to insert the total number of items

it.each(['first', 'second'])('test %K of %N', (x) => { ... })
// creates the tests
// "test 1 of 2"
// "test 2 of 2"

Example: it.each([10, 20, 30])('case %K: an item costs $%d.00 on sale', ...

Title function

You can form the test title yourself using a function. The function will get the item, the index, and all items and should return a string with the test title.

function makeTestTitle(s, k, strings) {
  return `test ${k + 1} for "${s}"`
}
it.each(['first', 'second'])(makeTestTitle, () => ...)
// creates the tests
// 'test 1 for "first"'
// 'test 2 for "second"'

It is very useful for forming a test title based on a property of an object, like

it.each([
  { name: 'Joe', age: 30 },
  { name: 'Mary', age: 20 },
])(
  (person) => `tests person ${person.name}`,
  (person) => { ... }
})
// creates the tests
// "tests person Joe"
// "tests person Mary"

See [cypress/integration/title-function.js](./cypress/integration/ title-function.js) for more examples

Every Nth item

You can quickly take every Nth item from an array

it.each(items, N)(...)

This is the same as taking the index of the item (zero-based) and doing k % N === 0

const items = [1, 2, 3, 4, 5, 6, ...]
it.each(items, 3)(...)
// tests item 1, 4, 7, ...

Chunking

There is a built-in chunking helper in describe.each and it.each to only take a subset of the items. For example, to split all items into 3 chunks, and take the middle one, use

it.each(items, 3, 1)(...)

The other spec files can take the other chunks. The index starts at 0, and should be less than the number of chunks.

// split all items among 3 specs
// spec-a.js
it.each(items, 3, 0)(...)
// spec-b.js
it.each(items, 3, 1)(...)
// spec-c.js
it.each(items, 3, 2)(...)

Sampling

Cypress bundles Lodash library which includes _.sampleSize method that you can use to randomly pick N items when passing the list to it.each

// pick 2 random items from the array and create 2 tests
it.each(Cypress._.sampleSize(items, 2))(...)

Custom filter predicate

You can filter the items by passing a predicate function

it.each(items, (x, k) => ...)
// creates a test for every item the predicate returns a truthy value

Return value

it.each(...)(...) and describe.each(...)(...) return the number of created tests.

const n = it.each([1, 2])(...)
// n is 2

Exclusive tests

Normally you could run just a selected test using it.only or a suite of tests using describe.only. Similarly, you could skip a single test or a suite of tests using it.skip and describe.skip methods. These methods are NOT supported by it.each and describe.each. Thus if you want to only run the it.each tests, surround it with its own describe block.

// only run the generated tests
describe.only('my tests', () => {
  it.each(items)(...)
})
// skip these tests
describe.skip('obsolete generated tests', () => {
  it.each(items)(...)
})
// run just these suites of generated tests
describe.only('my suites of tests', () => {
  describe.each(items)(...)
})

Test configuration object

Cypress allows to pass some of its configuration options in the it and describe arguments, see the configuration page. These methods it.each and describe.each do not support this, but you can create a wrapper describe block and set the options there, if needed.

// if a test inside this suite fails,
// retry it up to two times before failing it
describe('user', { retries: 2 }, () => {
  it.each(users)(...)
})

Run specs in parallel

See the explanation in the blog post Refactor Tests To Be Independent And Fast Using Cypress-Each Plugin, but basically you create separate specs file, and each just uses cypress-each to run a subset of the tests

// utils.js
export const testTitle = (selector, k) =>
  `testing ${k + 1} ...`

export const testDataItem = (item) => {
  ...
}

// spec1.js
import { data } from '...'
import { testTitle, testDataItem } from './utils'
it.each(data, 3, 0)(testTitle, testDataItem)

// spec2.js
import { data } from '...'
import { testTitle, testDataItem } from './utils'
it.each(data, 3, 1)(testTitle, testDataItem)

// spec3.js
import { data } from '...'
import { testTitle, testDataItem } from './utils'
it.each(data, 3, 2)(testTitle, testDataItem)

Test case object

Sometimes you just want to have a single object that has all the tests cases together with the inputs. You can pass an object instead of an array to the it.each function. Each object key will become the test title, and the value will be passed to the test callback. If the value is an array, it will be destructured. See object-input.cy.ts spec file for details.

const testCases = {
  // key: the test label
  // value: list of inputs for each test case
  'positive numbers': [1, 6, 7], // [a, b, expected result]
  'negative numbers': [1, -6, -5],
}
it.each(testCases)((a, b, expectedResult) => {
  expect(add(a, b)).to.equal(expectedResult)
})

test case types

Note that in most cases, the it.each(TestCases) tries to "guess" the types from the array value to the test callback function. When you need to, use the utility types to "explain" the value array:

// two arguments
// each value is [number, string]
const toString: TestCaseObject2<number, string> = {
  one: [1, '1'],
  ten: [10, '10'],
}

it.each(toString)((a, b) => {
  // a is a number
  // b is a string
})

// three arguments
const additions: TestCaseObject3<number, number, string> = {
  one: [1, 2, '3'], // a + b in string form
  ten: [10, 20, '30'],
}

it.each(additions)((a, b, s) => {
  expect(String(a + b)).to.equal(s)
})

Specs

Find the implementation in src/index.js

• it-spec.js uses no shortcuts to define multiple tests that are almost the same. We want to avoid the repetition
• it-each-spec.js uses the it.each helper to generate multiple it tests given a data array
• describe-each-spec.js uses describe.each helper to create describe blocks for each item in the given data array
• mocha-each-spec.js uses 3rd party mocha-each to generate it tests for each data item

Types

This package includes TypeScript definition for it.each and describe.each. Thus the parameter should be the right type from the array of values:

it.each([
  { name: 'Joe', age: 30 },
  { name: 'Mary', age: 20 },
])('has correct types', (user) => {
  // the type for the "user" should be
  // name: string, age: number
  expect(user).to.have.keys('name', 'age')
  expect(user.name).to.be.a('string')
  expect(user.age).to.be.a('number')
})

Include this module with other library types, like

{
  "compilerOptions": {
    "types": ["cypress", "cypress-each"]
  }
}

Or inside an individual spec file add

/// <reference types="cypress-each" />

Small print

Author: Gleb Bahmutov <gleb.bahmutov@gmail.com> © 2021

• @bahmutov
• glebbahmutov.com
• blog
• videos
• presentations
• cypress.tips

License: MIT - do anything with the code, but don't blame me if it does not work.

Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

Copyright (c) 2021 Gleb Bahmutov <gleb.bahmutov@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.