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Глобальные значения

В скриптах тестирования, Jest создает эти функции и объекты в глобальной области видимости. Вам не нужно ничего импортировать или подключать к скрипту для работы с этими функциями и объектами. Однако, если вы предпочитаете импорт, вы можете импортировать {describe, expect, test} из '@jest/globals'.

info

Примеры TypeScript с этой страницы будут работать только в том случае, если вы явно импортируете Jest API:

Import {expect, jest, test} from '@jest/globals';

Обратитесь к Началу работы за подробностями о том, как установить Jest с TypeScript.

Методы​

Справка​

afterAll(fn, timeout)​

Выполняет функцию после всех тестов в этом файле. Если функция возвращает промис или является генератором, Jest ждет пока промис разрешится, а затем запускает тесты.

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

Например:

Например:

const globalDatabase = makeGlobalDatabase();

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

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

test('может найти запись', () => {
  return globalDatabase.find('запись', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

test('может добавить запись', () => {
  return globalDatabase.insert('запись', makeThing(), response => {
    expect(response.success).toBeTruthy();
  });
});

Если afterAll находится внутри блока describe, то он запускается в конце блока describe.

Если вы хотите производить очистку после каждого теста, а не после всех тестов, то вместо этого используйте afterEach.

Это может быть полезно, если вы хотите очистить некоторое временное состояние создаваемое каждым тестом.

afterEach(fn, timeout)​

Выполняет функцию после каждого теста в файле. Если функция возвращает промис или является генератором, Jest ждет пока промис разрешится, а затем запускает тесты.

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

Например:

Например:

const globalDatabase = makeGlobalDatabase();

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

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

test('може найти запись', () => {
  return globalDatabase.find('запись', {}, results => {
    expect(results.length).toBeGreaterThan(0);
  });
});

test('может добавить запись', () => {
  return globalDatabase.insert('запись', makeThing(), response => {
    expect(response.success).toBeTruthy();
  });
});

Если afterEach находится внутри блока describe, то он запускается только после каждого теста внутри блока describe.

Если вы хотите провести очистку только один раз, после всех тестов, используйте afterAll.

Если вы хотите провести очистку только один раз, после всех тестов, используйте afterAll.

beforeAll(fn, timeout)​

Выполняет функцию перед запуском каждого теста в этом файле. Если функция возвращает промис или является генератором, Jest ждет пока промис разрешится, а затем запускает тест.

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

Например:

Например:

const globalDatabase = makeGlobalDatabase();

beforeEach(() => {
  // Очищает базу данных и добавляет данные тестирования.
  // Jest будет ждать завершения этого Promise перед запуском тестов.
  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();
  });
});

Здесь beforeAll гарантирует, что база данных настроена, перед запуском тестов. If setup was synchronous, you could do this without beforeAll. Ключевым является то, что Jest будет ждать разрешения промиса, поэтому вы можете установить асинхронно.

Если вместо запуска перед выполнением всех тестов, вы хотите что-то запускать перед каждым тестом, то используйте beforeEach.

Если вместо запуска перед выполнением всех тестов, вы хотите что-то запускать перед каждым тестом, то используйте beforeEach.

beforeEach(fn, timeout)​

Выполняет функцию перед выполнением тестов в текущем файле. Если функция возвращает промис или является генератором, Jest ждет пока промис разрешится, а затем запускает тесты.

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

This is often useful if you want to reset some global state that will be used by many tests.

Например:

const globalDatabase = makeGlobalDatabase();

beforeEach(() => {
  // Clears the database and adds some testing data.
  // Jest будет ждать завершения этого Promise перед запуском тестов.
  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);
  });
});

Here the beforeEach ensures that the database is reset for each test.

If beforeEach is inside a describe block, it runs for each test in the describe block.

If you only need to run some setup code once, before any tests run, use beforeAll instead.

describe(name, fn)​

describe(name, fn) группирует связанные по логике тесты в один блок. Например, если у вас есть объект myBeverage, который должен быть вкусным (ключ "delicious"), но не кислым (ключ "sour"), вы можете протестировать его следующим образом:

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

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

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

Это не обязательно, вы можете писать тесты в глобальном уровне. Но это может быть удобно, группировать некоторые тесты вместе.

You can also nest describe blocks if you have a hierarchy of tests:

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')).toThrow(CustomError);
    });

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

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

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

Используйте describe.each если собираетесь дублировать одинаковые тесты с разными данными. describe.each позволяет вам писать наборы тестов один раз и передавать в него данные.

describe.each is available with two APIs:

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

  • table: Массив of Arrays with the arguments that are passed into the fn for each row. 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]].

  • наименование: Строка название теста.

    • 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.
      • %$ - Number of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
    • Or generate unique test titles by injecting properties of test case object with $variable
      • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
      • You can use $# to inject the index of the test case
      • You cannot use $variable with the printf formatting except for %%

  • fn: Function the suite of tests to be run, 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. The default timeout is 5 seconds.

Пример:

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 ${expected}`, () => {
    expect(a + b).not.toBeLessThan(expected);
  });
});
describe.each([
  {a: 1, b: 1, expected: 2},
  {a: 1, b: 2, expected: 3},
  {a: 2, b: 1, expected: 3},
])('.add($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);
  });
});

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.
  • name: String the title of the test suite, use $variable to inject test data into the suite title from the tagged template expressions, and $# for the index of the row.
    • 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 run, 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. The default timeout is 5 seconds.

Пример:

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

  test(`возвращаемое значение не должно быть больше чем ${expected}`, () => {
    expect(a + b).not.toBeGreaterThan(expected);
  });

  test(`возвращаемое значение не должно быть меньше чем ${expected}`, () => {
    expect(a + b).not.toBeLessThan(expected);
  });
});

describe.only(name, fn)​

Also under the alias: fdescribe(name, fn)

You can use describe.only if you want to run only one describe block:

describe.only('мой напиток', () => {
  test('вкусный', () => {
    expect(myBeverage.delicious).toBeTruthy();
  });

  test('не кислый', () => {
    expect(myBeverage.sour).toBeFalsy();
  });
});

describe('мои другие напитки', () => {
// будет пропущено
});

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 run', () => {
  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 to $b', ({a, b, expected}) => {
  test('passes', () => {
    expect(a + b).toBe(expected);
  });
});

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

describe.skip(name, fn)​

Also under the alias: xdescribe(name, fn)

You can use describe.skip if you do not want to run the tests of a particular describe block:

describe('мой напиток', () => {
  test('вкусный', () => {
    expect(myBeverage.delicious).toBeTruthy();
  });

  test('не кислый', () => {
    expect(myBeverage.sour).toBeFalsy();
  });
});

describe.skip('мои другие напитки', () => {
  // ... будет пропущено
});

Using describe.skip is often a cleaner alternative to temporarily commenting out a chunk of tests. Beware that the describe block will still run. If you have some setup that also should be skipped, do it in a beforeAll or beforeEach block.

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 run
  });
});

test('will be run', () => {
  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 to $b', ({a, b, expected}) => {
  test('will not be run', () => {
    expect(a + b).toBe(expected); // will not be run
  });
});

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

test(name, fn, timeout)​

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

All you need in a test file is the test method which runs a test. For example, let's say there's a function inchesOfRain() that should be zero. Your whole test could be:

test('дождя не было', () => {
  expect(inchesOfRain()).toBe(0);
});

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

If a promise is returned from test, Jest will wait for the promise to resolve before letting the test complete. For example, let's say fetchBeverageList() returns a promise that is supposed to resolve to a list that has lemon in it. You can write:

test('содержит ли лимон', () => {
  return fetchBeverageList().then(list => {
    expect(list).toContain('lemon');
  });
});

Even though the call to test will return right away, the test doesn't complete until the promise resolves. For more details, see Testing Asynchronous Code page.

tip

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.

test.concurrent(name, fn, timeout)​

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

caution

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

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

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. 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);
});
tip

Use the maxConcurrency configuration option to prevent 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)

Используйте test.concurrent.each если собираетесь дублировать одинаковые тесты с разными данными. 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: Массив of Arrays with the arguments that are passed into the test fn for each row. 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]]
  • наименование: Строка 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.
      • %$ - Number of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
  • fn: Function the test to be run, 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. The default timeout is 5 seconds.

Пример:

test.concurrent.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', async (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.
  • наименование: Строка 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 run, 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. The default timeout is 5 seconds.

Пример:

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

test('will not be run', () => {
  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 run
});

test('will be run', () => {
  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 to $b', async ({a, b, expected}) => {
  expect(a + b).toBe(expected); // will not be run
});

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

test.each(table)(name, fn, timeout)​

Можно воспользоваться алиасами: it.each(table)(name, fn) и it.each`table`(name, fn)

Используйте test.each если собираетесь дублировать одинаковые тесты с разными данными. test.each позволяет вам писать тест один раз и передавать в него данные.

test.each is available with two APIs:

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

  • table: Массив of Arrays with the arguments that are passed into the test fn for each row. 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]]
  • наименование: Строка 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.
      • %$ - Number of the test case.
      • %% - single percent sign ('%'). This does not consume an argument.
    • Or generate unique test titles by injecting properties of test case object with $variable
      • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
      • You can use $# to inject the index of the test case
      • You cannot use $variable with the printf formatting except for %%
  • fn: Function the test to be run, 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. The default timeout is 5 seconds.

Пример:

test.each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
])('.add(%i, %i)', (a, b, expected) => {
  expect(a + b).toBe(expected);
});
test.each([
  {a: 1, b: 1, expected: 2},
  {a: 1, b: 2, expected: 3},
  {a: 2, b: 1, expected: 3},
])('.add($a, $b)', ({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.
  • наименование: Строка 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 run, 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. The default timeout is 5 seconds.

Пример:

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

test.failing(name, fn, timeout)​

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

note

This is only available with the default jest-circus runner.

Use test.failing when you are writing a test and expecting it to fail. These tests will behave the other way normal tests do. If failing test will throw any errors then it will pass. If it does not throw it will fail.

tip

You can use this type of test i.e. when writing code in a BDD way. In that case the tests will not show up as failing until they pass. Then you can just remove the failing modifier to make them pass.

It can also be a nice way to contribute failing tests to a project, even if you don't know how to fix the bug.

Пример:

test.failing('it is not equal', () => {
  expect(5).toBe(6); // this test will pass
});

test.failing('it is equal', () => {
  expect(10).toBe(10); // this test will fail
});

test.failing.each(name, fn, timeout)​

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

note

This is only available with the default jest-circus runner.

You can also run multiple tests at once by adding each after failing.

Пример:

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

test.only.failing(name, fn, timeout)​

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

note

This is only available with the default jest-circus runner.

Use test.only.failing if you want to only run a specific failing test.

test.skip.failing(name, fn, timeout)​

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

note

This is only available with the default jest-circus runner.

Use test.skip.failing if you want to skip running a specific failing test.

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 for each row before aborting. The default timeout is 5 seconds.

For example, let's say you had these tests:

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 run', () => {
  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 to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

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

test.skip(name, fn)​

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

When you are maintaining a large codebase, you may sometimes find a test that is temporarily broken for some reason. 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.

For example, let's say you had these tests:

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

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

Only the "it is raining" test will run, since the other test is run with 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 run
});

test('will be run', () => {
  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 to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected); // will not be run
});

test('will be run', () => {
  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.

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

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

test.todo will throw an error if you pass it a test callback function. Use test.skip instead, if you already implemented the test, but do not want it to run.

TypeScript Usage​

info

Примеры TypeScript с этой страницы будут работать только в том случае, если вы явно импортируете Jest API:

Import {expect, jest, test} from '@jest/globals';

Обратитесь к Началу работы за подробностями о том, как установить Jest с TypeScript.

.each​

The .each modifier offers few different ways to define a table of the test cases. Some of the APIs have caveats related with the type inference of the arguments which are passed to describe or test callback functions. Let's take a look at each of them.

note

For simplicity test.each is picked for the examples, but the type inference is identical in all cases where .each modifier can be used: describe.each, test.concurrent.only.each, test.skip.each, etc.

Array of objects​

The array of objects API is most verbose, but it makes the type inference a painless task. A table can be inlined:

import {test} from '@jest/globals';

test.each([
  {name: 'a', path: 'path/to/a', count: 1, write: true},
  {name: 'b', path: 'path/to/b', count: 3},
])('inline table', ({name, path, count, write}) => {
  // arguments are typed as expected, e.g. `write: boolean | undefined`
});

Or declared separately as a variable:

import {test} from '@jest/globals';

const table = [
  {a: 1, b: 2, expected: 'three', extra: true},
  {a: 3, b: 4, expected: 'seven', extra: false},
  {a: 5, b: 6, expected: 'eleven'},
];

test.each(table)('table as a variable', ({a, b, expected, extra}) => {
  // again everything is typed as expected, e.g. `extra: boolean | undefined`
});

Array of arrays​

The array of arrays style will work smoothly with inlined tables:

import {test} from '@jest/globals';

test.each([
  [1, 2, 'three', true],
  [3, 4, 'seven', false],
  [5, 6, 'eleven'],
])('inline table example', (a, b, expected, extra) => {
  // arguments are typed as expected, e.g. `extra: boolean | undefined`
});

However, if a table is declared as a separate variable, it must be typed as an array of tuples for correct type inference (this is not needed only if all elements of a row are of the same type):

import {test} from '@jest/globals';

const table: Array<[number, number, string, boolean?]> = [
  [1, 2, 'three', true],
  [3, 4, 'seven', false],
  [5, 6, 'eleven'],
];

test.each(table)('table as a variable example', (a, b, expected, extra) => {
  // without the annotation types are incorrect, e.g. `a: number | string | boolean`
});

Template literal​

If all input values are of the same type, the template literal API will type the arguments correctly:

import {test} from '@jest/globals';

test.each`
  a    | b    | expected
  ${1} | ${2} | ${3}
  ${3} | ${4} | ${7}
  ${5} | ${6} | ${11}
`('template literal example same type', ({a, b, expected}) => {
  // all arguments are of type `number` because all inputs (a, b, expected) are of type `number`
});

If the inputs have different types, the arguments will be typed as a union of all the input types (i.e. type of the variables inside the template literal):

import {test} from '@jest/globals';

test.each`
  a    | b    | expected
  ${1} | ${2} | ${'three'}
  ${3} | ${4} | ${'seven'}
  ${5} | ${6} | ${'eleven'}
`('template literal example different types', ({a, b, expected}) => {
  // all arguments are of type `number | string` because some inputs (a, b) are of type `number` and some others (expected) are of type `string`
});

Otherwise, if you want each argument to have the right type, you have to explicitly provide the generic type argument:

import {test} from '@jest/globals';

test.each<{a: number; b: number; expected: string; extra?: boolean}>`
  a    | b    | expected    | extra
  ${1} | ${2} | ${'three'}  | ${true}
  ${3} | ${4} | ${'seven'}  | ${false}
  ${5} | ${6} | ${'eleven'}
`('template literal example', ({a, b, expected, extra}) => {
  // all arguments are typed as expected, e.g. `a: number`, `expected: string`, `extra: boolean | undefined`
});
caution

Keep in mind the variables inside the template literal are not type checked, so you have to ensure that their types are correct.

import {test} from '@jest/globals';

test.each<{a: number; expected: string}>`
  a                            | expected
  ${1}                         | ${'one'}
  ${'will not raise TS error'} | ${'two'}
  ${3}                         | ${'three'}
`('template literal with wrongly typed input', ({a, expected}) => {
  // all arguments are typed as stated in the generic: `a: number`, `expected: string`
  // WARNING: `a` is of type `number` but will be a string in the 2nd test case.
});