Version: 25.x

Globales

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'.

Métodos

afterAll(fn, tiempo)
afterEach(fn, tiempo)
beforeAll(fn, tiempo)
beforeEach(fn, tiempo)
describe(name, fn)
describe.each(table)(name, fn, timeout)
describe.only(name, fn)
describe.only.each(table)(name, fn)
describe.skip(name, fn)
describe.skip.each(table)(name, fn)
prueba(nombre, fn, tiempo)
test.each(table)(name, fn, timeout)
test.only(name, fn, tiempo)
test.only.each(table)(name, fn)
test.skip(name, fn)
test.skip.each(table)(name, fn)
test.todo(name)

Referencia

`afterAll(fn, tiempo)`

Ejecuta una función después de que todos los test en este archivo se hayan completado. Si la función devuelve una promesa o es una función generadora, Jest espera a que la promesa se resuelva antes de continuar.

Opcionalmente, puedes pasar un tiempo (en milisegundos) especificando cuanto esperar antes de abortar. The default timeout is 5 seconds.

Por ejemplo:

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();
  });
});

Si afterAll es llamado dentro de un bloque describe, este se ejecutará al final de la ejecución del bloque describe.

Si se desea ejecutar algún tipo de limpieza o restablecimiento después de cada prueba en lugar de al final de todas las pruebas, se puede utilizar afterEach.

`afterEach(fn, tiempo)`

Runs a function after each one of the tests in this file completes. Si la función devuelve una promesa o es una función generadora, Jest espera a que la promesa se resuelva antes de continuar.

Opcionalmente, puedes pasar un tiempo (en milisegundos) especificando cuanto esperar antes de abortar. The default timeout is 5 seconds.

Por ejemplo:

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();
  });
});

Si afterAll es llamado dentro de un bloque describe, este se ejecutará al final de la ejecución de cada prueba en el bloque describe.

Si se desea ejecutar algún tipo de limpieza o restablecimiento una sola vez por todas las pruebas, se puede utilizar afterAll.

`beforeAll(fn, tiempo)`

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.

Opcionalmente, puedes pasar un tiempo (en milisegundos) especificando cuanto esperar antes de abortar. The default timeout is 5 seconds.

Por ejemplo:

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();
  });
});

Aquí el bloque beforeAll garantiza que la base de datos sea configurada antes de que se ejecuten las pruebas. If setup was synchronous, you could do this without beforeAll. La clave es que Jest espera a una promise para resolver, de modo que también se puede tener configuración inicial setup asincrona.

Si se desea ejecutar código antes de cada prueba en lugar de antes de todas las pruebas, se puede usar beforeEach.

`beforeEach(fn, tiempo)`

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.

Opcionalmente, puedes pasar un tiempo (en milisegundos) especificando cuanto esperar antes de abortar. The default timeout is 5 seconds.

Por ejemplo:

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);
  });
});

Si el bloque beforeAll se encuentra dentro de un bloque describe, esté se ejecutará una vez antes de cada prueba en el bloque describe.

Si se desea ejecutar código de configuración inicial, una sola vez antes de cualquier prueba, usesé beforeAll.

`describe(name, fn)`

describe(name, fn) creates a block that groups together several related tests. Por ejemplo, si se tiene una objeto myBeverage que representa una bebida que debe ser deliciosa pero no agria, se podría probar con:

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.

También se pueden anidar bloques describe si se tiene una jerarquía de pruebas:

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)`

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. 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]].
name: String 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 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.

Ejemplo:

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.
name: String 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 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.

Ejemplo:

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)`

Se puede utilizar describe.only si se desea ejecutar solo ún bloque describe:

Si el bloque beforeAll se encuentra dentro de un bloque describe, esté se ejecutará al principio del bloque describe.

describe.only('mi bebida', () => {
  test('es deliciosa', () => {
    expect(miBebida.deliciosa).toBeTruthy();
  });

  test('no es amarga', () => {
    expect(miBebida.amarga).toBeFalsy();
  });
});

describe('mi otra bebida', () => {
  // ... 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 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)`

Se puede utilizar describe.skip si se desea omitirun bloque describe en particular:

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

describe('mi bebida', () => {
  test('es deliciosa', () => {
    expect(miBebida.deliciosa).toBeTruthy();
  });

  test('no es amarga', () => {
    expect(miBebida.amarga).toBeFalsy();
  });
});

describe.skip('mi otra bebida', () => {
  // ... will be skipped
});

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);
});

`prueba(nombre, fn, tiempo)`

También con el alias: it(name, fn, tiempo)

Todo lo que se requiere en un archivo de prueba es el metodo test para ejecutar una prueba. Por ejemplo, se asume una función que mide las pulgadas de lluvia inchesOfRain() debe regresar cero. La prueba completa sería:

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

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.

If a promise is returned from test, Jest will wait for the promise to resolve before letting the test complete. Por ejemplo, se asume una función que regresa una lista de bebidas fetchBeverageList(). Si esta función regresa una promise que se resuelve a una lista que contiene lemon. Podemos probarlo con:

test('has lemon in it', () => {
  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.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. 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]]
name: String 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 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.

Ejemplo:

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.
name: String 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.

Ejemplo:

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.only(name, fn, tiempo)`

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.

Opcionalmente, puedes pasar un tiempo (en milisegundos) especificando cuanto esperar antes de abortar. The default timeout is 5 seconds.

Por ejemplo, digamos que se tuviera estas pruebas:

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)

Cuando se trabaja en una gran base de código, es frecuente encontrar alguna prueba que falla de manera temporal. 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.

Por ejemplo, digamos que se tuviera estas pruebas:

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

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

Sólo se ejecutaría la prueba "it is raning", pues se agregó test.skip a la otra prueba.

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.

Métodos​

Referencia​

afterAll(fn, tiempo)​

afterEach(fn, tiempo)​

beforeAll(fn, tiempo)​

beforeEach(fn, tiempo)​

describe(name, fn)​

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

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

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

describe.only(name, fn)​

describe.only.each(table)(name, fn)​

describe.only.each(table)(name, fn)​

describe.only.each`table`(name, fn)​

describe.skip(name, fn)​

describe.skip.each(table)(name, fn)​

describe.skip.each(table)(name, fn)​

describe.skip.each`table`(name, fn)​

prueba(nombre, fn, tiempo)​

test.each(table)(name, fn, timeout)​

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

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

test.only(name, fn, tiempo)​

test.only.each(table)(name, fn)​

test.only.each(table)(name, fn)​

test.only.each`table`(name, fn)​

test.skip(name, fn)​

test.skip.each(table)(name, fn)​

test.skip.each(table)(name, fn)​

test.skip.each`table`(name, fn)​

test.todo(name)​

Métodos

Referencia

`afterAll(fn, tiempo)`

`afterEach(fn, tiempo)`

`beforeAll(fn, tiempo)`

`beforeEach(fn, tiempo)`

`describe(name, fn)`

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

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

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

`describe.only(name, fn)`

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

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

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

`describe.skip(name, fn)`

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

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

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

`prueba(nombre, fn, tiempo)`

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

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

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

`test.only(name, fn, tiempo)`

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

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

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

`test.skip(name, fn)`

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

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

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

`test.todo(name)`