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Globals

In your test files, Jest puts each of these methods and objects into the global environment. You don't have to require or import anything to use them. However, if you prefer explicit imports, you can do import {describe, expect, test} from '@jest/globals'.

Методи

Довідка

afterAll(fn, timeout)

Runs a function after all the tests in this file have completed. If the function returns a promise or is a generator, Jest waits for that promise to resolve before continuing.

Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Це часто буває корисним якщо ви хочете очистити певний глобальний стан, спільний для різних тестів.

Наприклад:

const globalDatabase = makeGlobalDatabase();

function cleanUpDatabase(db) {
  db.cleanUp();
}

afterAll(() => {
  cleanUpDatabase(globalDatabase);
});

test('can find things', () => {
  return globalDatabase.find('thing', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

test('can insert a thing', () => {
  return globalDatabase.insert('thing', makeThing(), response => {
    expect(response.success).toBeTruthy();
  });
});

Тут afterAll гарантує, що cleanUpDatabase викликається після того, як виконаються всі тести.

Якщо afterAll знаходиться всередині блоку describe, він виконується в кінці цього блоку тестів.

Якщо ви хочете виконувати очистку після кожного тесту, використовуйте afterEach взамін.

afterEach(fn, timeout)

Runs a function after each one of the tests in this file completes. If the function returns a promise or is a generator, Jest waits for that promise to resolve before continuing.

Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Це часто буває корисним якщо ви хочете очистити певний тимчасовий стан, створений кожним з тестів.

Наприклад:

const globalDatabase = makeGlobalDatabase();

function cleanUpDatabase(db) {
  db.cleanUp();
}

afterEach(() => {
  cleanUpDatabase(globalDatabase);
});

test('can find things', () => {
  return globalDatabase.find('thing', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

test('can insert a thing', () => {
  return globalDatabase.insert('thing', makeThing(), response => {
    expect(response.success).toBeTruthy();
  });
});

Тут afterEach гарантує, що cleanUpDatabase викликається після виконання кожного тесту.

Якщо afterEach знаходиться всередині блоку describe, він виконується лише після кожного тесту всередині цього блоку.

Якщо ви хочете виконувати певну очистку тільки один раз після виконання всіх тестів, використовуйте afterAll.

beforeAll(fn, timeout)

Runs a function before any of the tests in this file run. If the function returns a promise or is a generator, Jest waits for that promise to resolve before running tests.

Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Це часто буває корисним якщо ви хочете встановити певний глобальний стан, який буде використовуватися кількома тестами.

Наприклад:

const globalDatabase = makeGlobalDatabase();

beforeAll(() => {
  // Clears the database and adds some testing data.
  // Jest will wait for this promise to resolve before running tests.
  return globalDatabase.clear().then(() => {
    return globalDatabase.insert({testData: 'foo'});
  });
});

// Since we only set up the database once in this example, it's important
// that our tests don't modify it.
test('can find things', () => {
  return globalDatabase.find('thing', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

Тут beforeAll гарантує, що база даних буде створена, перш ніж запускати тести. If setup was synchronous, you could do this without beforeAll. Основна перевага полягає в тому, що Jest чекатиме, поки виконається проміс, що дозволяє використання асинхронних налаштувань.

Якщо beforeAll знаходиться всередині блоку describe, він виконується на початку цього блоку тестів.

Якщо ви хочете виконувати якісь команди перед запуском кожного тесту, використовуйте beforeEach взамін.

beforeEach(fn, timeout)

Runs a function before each of the tests in this file runs. If the function returns a promise or is a generator, Jest waits for that promise to resolve before running the test.

Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Це часто буває корисним якщо ви хочете перевстановити певний глобальний стан, який буде використовуватися кількома тестами.

Наприклад:

const globalDatabase = makeGlobalDatabase();

beforeEach(() => {
  // Clears the database and adds some testing data.
  // Jest will wait for this promise to resolve before running tests.
  return globalDatabase.clear().then(() => {
    return globalDatabase.insert({testData: 'foo'});
  });
});

test('can find things', () => {
  return globalDatabase.find('thing', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

test('can insert a thing', () => {
  return globalDatabase.insert('thing', makeThing(), response => {
    expect(response.success).toBeTruthy();
  });
});

Тут beforeEach гарантує, що база даних буде створена заново перед кожним тестом.

Якщо beforeEach знаходиться всередині блоку describe, він виконується перед кожним тестом в цьому блоці.

Якщо вам потрібно виконати певні налаштування лише один раз перед запуском всіх тестів, використовуйте beforeAll взамін.

describe(name, fn)

describe(name, fn) creates a block that groups together several related tests. Наприклад, якщо у вас є об’єкт myBeverage який повинен мати властивість delicious і не мати властивості sour, ви можете протестувати це так:

const myBeverage = {
  delicious: true,
  sour: false,
};

describe('my beverage', () => {
  test('is delicious', () => {
    expect(myBeverage.delicious).toBeTruthy();
  });

  test('is not sour', () => {
    expect(myBeverage.sour).toBeFalsy();
  });
});

This isn't required - you can write the test blocks directly at the top level. But this can be handy if you prefer your tests to be organized into groups.

Ви також можете вкладати блоки describe один в одного якщо у вас є ієрахія тестів:

const binaryStringToNumber = binString => {
  if (!/^[01]+$/.test(binString)) {
    throw new CustomError('Not a binary number.');
  }

  return parseInt(binString, 2);
};

describe('binaryStringToNumber', () => {
  describe('given an invalid binary string', () => {
    test('composed of non-numbers throws CustomError', () => {
      expect(() => binaryStringToNumber('abc')).toThrowError(CustomError);
    });

    test('with extra whitespace throws CustomError', () => {
      expect(() => binaryStringToNumber('  100')).toThrowError(CustomError);
    });
  });

  describe('given a valid binary string', () => {
    test('returns the correct number', () => {
      expect(binaryStringToNumber('100')).toBe(4);
    });
  });
});

describe.each(table)(name, fn, timeout)

Use describe.each if you keep duplicating the same test suites with different data. describe.each allows you to write the test suite once and pass data in.

describe.each is available with two APIs:

1. describe.each(table)(name, fn, timeout)

  • table: Array of Arrays with the arguments that are passed into the fn for each row.
    • Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e. [1, 2, 3] -> [[1], [2], [3]]
  • назва: Рядок the title of the test suite.
    • Generate unique test titles by positionally injecting parameters with printf formatting:
      • %p - pretty-format.
      • %s- String.
      • %d- Number.
      • %i - Integer.
      • %f - Floating point value.
      • %j - JSON.
      • %o - Object.
      • %# - Index of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
  • fn: Function the suite of tests to be ran, this is the function that will receive the parameters in each row as function arguments.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

describe.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });

  test(`returned value not be greater than ${expected}`, () => {
    expect(a + b).not.toBeGreaterThan(expected);
  });

  test(`returned value not be less than ${expected}`, () => {
    expect(a + b).not.toBeLessThan(expected);
  });
});

2. describe.each`table`(name, fn, timeout)

  • table: Tagged Template Literal
    • First row of variable name column headings separated with |
    • One or more subsequent rows of data supplied as template literal expressions using ${value} syntax.
  • назва: Рядок the title of the test suite, use $variable to inject test data into the suite title from the tagged template expressions.
    • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
  • fn: Function the suite of tests to be ran, this is the function that will receive the test data object.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

describe.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('$a + $b', ({a, b, expected}) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });

  test(`returned value not be greater than ${expected}`, () => {
    expect(a + b).not.toBeGreaterThan(expected);
  });

  test(`returned value not be less than ${expected}`, () => {
    expect(a + b).not.toBeLessThan(expected);
  });
});

describe.only(name, fn)

Також має псевдонім fdescribe(name, fn)

Ви можете використовувати describe.only, якщо ви хочете виконати лише один блок describe:

describe.only('my beverage', () => {
  test('is delicious', () => {
    expect(myBeverage.delicious).toBeTruthy();
  });

  test('is not sour', () => {
    expect(myBeverage.sour).toBeFalsy();
  });
});

describe('my other beverage', () => {
  // ... will be skipped
});

describe.only.each(table)(name, fn)

Also under the aliases: fdescribe.each(table)(name, fn) and fdescribe.each`table`(name, fn)

Use describe.only.each if you want to only run specific tests suites of data driven tests.

describe.only.each is available with two APIs:

describe.only.each(table)(name, fn)

describe.only.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

describe.only.each`table`(name, fn)

describe.only.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  test('passes', () => {
    expect(a + b).toBe(expected);
  });
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

describe.skip(name, fn)

Також має псевдонім xdescribe(name, fn)

Ви можете використовувати describe.skip, якщо ви не хочете запускати тести з певного блоку describe:

describe('my beverage', () => {
  test('is delicious', () => {
    expect(myBeverage.delicious).toBeTruthy();
  });

  test('is not sour', () => {
    expect(myBeverage.sour).toBeFalsy();
  });
});

describe.skip('my other beverage', () => {
  // ... will be skipped
});

Using describe.skip is often a cleaner alternative to temporarily commenting out a chunk of tests.

describe.skip.each(table)(name, fn)

Also under the aliases: xdescribe.each(table)(name, fn) and xdescribe.each`table`(name, fn)

Use describe.skip.each if you want to stop running a suite of data driven tests.

describe.skip.each is available with two APIs:

describe.skip.each(table)(name, fn)

describe.skip.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected); // will not be ran
  });
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

describe.skip.each`table`(name, fn)

describe.skip.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  test('will not be ran', () => {
    expect(a + b).toBe(expected); // will not be ran
  });
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test(name, fn, timeout)

Also under the alias: it(name, fn, timeout)

Все, що вам потрібно в файлі з тестами - це метод test, який запускає тести. Наприклад, увімо, що є функція inchesOfRain(), яка повинна повертати нуль. Ваш тест може бути таким:

test('did not rain', () => {
  expect(inchesOfRain()).toBe(0);
});

Перший аргумент - це назва тесту, другий - функція, яка містить очікування, які потрібно перевірити. The third argument (optional) is timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Note: If a promise is returned from test, Jest will wait for the promise to resolve before letting the test complete. Jest will also wait if you provide an argument to the test function, usually called done. This could be handy when you want to test callbacks. See how to test async code here.

Наприклад, нехай fetchBeverageList() повертає проміс, який повинен виконатися зі списком, що містить lemon:

test('has lemon in it', () => {
  return fetchBeverageList().then(list => {
    expect(list).toContain('lemon');
  });
});

Незважаючи на те, що test відразу поверне значення, тест не буде виконано, поки не буде виконано проміс.

test.concurrent(name, fn, timeout)

Also under the alias: it.concurrent(name, fn, timeout)

Use test.concurrent if you want the test to run concurrently.

Note: test.concurrent is considered experimental - see here for details on missing features and other issues

The first argument is the test name; the second argument is an asynchronous function that contains the expectations to test. The third argument (optional) is timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

test.concurrent('addition of 2 numbers', async () => {
  expect(5 + 3).toBe(8);
});

test.concurrent('subtraction 2 numbers', async () => {
  expect(5 - 3).toBe(2);
});

Note: Use maxConcurrency in configuration to prevents Jest from executing more than the specified amount of tests at the same time

test.concurrent.each(table)(name, fn, timeout)

Also under the alias: it.concurrent.each(table)(name, fn, timeout)

Use test.concurrent.each if you keep duplicating the same test with different data. test.each allows you to write the test once and pass data in, the tests are all run asynchronously.

test.concurrent.each is available with two APIs:

1. test.concurrent.each(table)(name, fn, timeout)

  • table: Array of Arrays with the arguments that are passed into the test fn for each row.
    • Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e. [1, 2, 3] -> [[1], [2], [3]]
  • назва: Рядок the title of the test block.
    • Generate unique test titles by positionally injecting parameters with printf formatting:
      • %p - pretty-format.
      • %s- String.
      • %d- Number.
      • %i - Integer.
      • %f - Floating point value.
      • %j - JSON.
      • %o - Object.
      • %# - Index of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
  • fn: Function the test to be ran, this is the function that will receive the parameters in each row as function arguments, this will have to be an asynchronous function.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

test.concurrent.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  expect(a + b).toBe(expected);
});

2. test.concurrent.each`table`(name, fn, timeout)

  • table: Tagged Template Literal
    • First row of variable name column headings separated with |
    • One or more subsequent rows of data supplied as template literal expressions using ${value} syntax.
  • назва: Рядок the title of the test, use $variable to inject test data into the test title from the tagged template expressions.
    • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
  • fn: Function the test to be ran, this is the function that will receive the test data object, this will have to be an asynchronous function.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

test.concurrent.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

test.concurrent.only.each(table)(name, fn)

Also under the alias: it.concurrent.only.each(table)(name, fn)

Use test.concurrent.only.each if you want to only run specific tests with different test data concurrently.

test.concurrent.only.each is available with two APIs:

test.concurrent.only.each(table)(name, fn)

test.concurrent.only.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', async (a, b, expected) => {
  expect(a + b).toBe(expected);
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.only.each`table`(name, fn)

test.concurrent.only.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', async ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.concurrent.skip.each(table)(name, fn)

Also under the alias: it.concurrent.skip.each(table)(name, fn)

Use test.concurrent.skip.each if you want to stop running a collection of asynchronous data driven tests.

test.concurrent.skip.each is available with two APIs:

test.concurrent.skip.each(table)(name, fn)

test.concurrent.skip.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', async (a, b, expected) => {
  expect(a + b).toBe(expected); // will not be ran
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.concurrent.skip.each`table`(name, fn)

test.concurrent.skip.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', async ({a, b, expected}) => {
  expect(a + b).toBe(expected); // will not be ran
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.each(table)(name, fn, timeout)

Also under the alias: it.each(table)(name, fn) and it.each`table`(name, fn)

Use test.each if you keep duplicating the same test with different data. test.each allows you to write the test once and pass data in.

test.each is available with two APIs:

1. test.each(table)(name, fn, timeout)

  • table: Array of Arrays with the arguments that are passed into the test fn for each row.
    • Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e. [1, 2, 3] -> [[1], [2], [3]]
  • назва: Рядок the title of the test block.
    • Generate unique test titles by positionally injecting parameters with printf formatting:
      • %p - pretty-format.
      • %s- String.
      • %d- Number.
      • %i - Integer.
      • %f - Floating point value.
      • %j - JSON.
      • %o - Object.
      • %# - Index of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
  • fn: Function the test to be ran, this is the function that will receive the parameters in each row as function arguments.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

test.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  expect(a + b).toBe(expected);
});

2. test.each`table`(name, fn, timeout)

  • table: Tagged Template Literal
    • First row of variable name column headings separated with |
    • One or more subsequent rows of data supplied as template literal expressions using ${value} syntax.
  • назва: Рядок the title of the test, use $variable to inject test data into the test title from the tagged template expressions.
    • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
  • fn: Function the test to be ran, this is the function that will receive the test data object.
  • Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait for each row before aborting. Note: The default timeout is 5 seconds.

Приклад:

test.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

test.only(name, fn, timeout)

Also under the aliases: it.only(name, fn, timeout), and fit(name, fn, timeout)

When you are debugging a large test file, you will often only want to run a subset of tests. You can use .only to specify which tests are the only ones you want to run in that test file.

Optionally, you can provide a timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Наприклад, нехай у вас є наступні тести:

test.only('it is raining', () => {
  expect(inchesOfRain()).toBeGreaterThan(0);
});

test('it is not snowing', () => {
  expect(inchesOfSnow()).toBe(0);
});

Only the "it is raining" test will run in that test file, since it is run with test.only.

Usually you wouldn't check code using test.only into source control - you would use it for debugging, and remove it once you have fixed the broken tests.

test.only.each(table)(name, fn)

Also under the aliases: it.only.each(table)(name, fn), fit.each(table)(name, fn), it.only.each`table`(name, fn) and fit.each`table`(name, fn)

Use test.only.each if you want to only run specific tests with different test data.

test.only.each is available with two APIs:

test.only.each(table)(name, fn)

test.only.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  expect(a + b).toBe(expected);
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.only.each`table`(name, fn)

test.only.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

test('will not be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.skip(name, fn)

Also under the aliases: it.skip(name, fn), xit(name, fn), and xtest(name, fn)

Коли ви підтримуєте велику кодову базу, інколи може з’явитися, який тимчасово зламаний з якихось причин. If you want to skip running this test, but you don't want to delete this code, you can use test.skip to specify some tests to skip.

Наприклад, нехай у вас є наступні тести:

test('it is raining', () => {
  expect(inchesOfRain()).toBeGreaterThan(0);
});

test.skip('it is not snowing', () => {
  expect(inchesOfSnow()).toBe(0);
});

Лише тест "it is raining" буде виконано, оскільки інший тест запускається з test.skip.

You could comment the test out, but it's often a bit nicer to use test.skip because it will maintain indentation and syntax highlighting.

test.skip.each(table)(name, fn)

Also under the aliases: it.skip.each(table)(name, fn), xit.each(table)(name, fn), xtest.each(table)(name, fn), it.skip.each`table`(name, fn), xit.each`table`(name, fn) and xtest.each`table`(name, fn)

Use test.skip.each if you want to stop running a collection of data driven tests.

test.skip.each is available with two APIs:

test.skip.each(table)(name, fn)

test.skip.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  expect(a + b).toBe(expected); // will not be ran
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.skip.each`table`(name, fn)

test.skip.each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`('returns $expected when $a is added $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected); // will not be ran
});

test('will be ran', () => {
  expect(1 / 0).toBe(Infinity);
});

test.todo(name)

Also under the alias: it.todo(name)

Use test.todo when you are planning on writing tests. These tests will be highlighted in the summary output at the end so you know how many tests you still need todo.

Note: If you supply a test callback function then the test.todo will throw an error. If you have already implemented the test and it is broken and you do not want it to run, then use test.skip instead.

API

  • name: String the title of the test plan.

Приклад:

const add = (a, b) => a + b;

test.todo('add should be associative');
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