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Version: 25.x

Globale

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'.

Metode#


Reference#

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.

De exemplu:

De exemplu:

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();
});
});

În cazul în care afterAll este în interiorul unui bloc describe, se va executa la sfârşitul blocului.

Dacă doriţi să rulaţi ceva logică de curățare după fiecare test, nu după toate testele, se poate utiliza afterEach în schimb.

Dacă doriţi să rulaţi ceva logică de curățare după fiecare test, nu după toate testele, se poate utiliza afterEach în schimb.

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.

De exemplu:

De exemplu:

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();
});
});

În cazul în care afterEach este în interiorul unui bloc describe, se va executa doar după fiecare test din interiorul blocului.

Dacă doriţi să rulaţi ceva logică de curățare doar o singură dată, după execuția tuturor testelor, utilizaţi afterAll în schimb.

Dacă doriţi să rulaţi ceva logică de curățare doar o singură dată, după execuția tuturor testelor, utilizaţi afterAll în schimb.

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.

De exemplu:

De exemplu:

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);
});
});

Aici beforeAll asigură că baza de date este setată înainte de a rula testele. If setup was synchronous, you could do this without beforeAll. Cheia este că Jest va aştepta pentru un Promise să se rezolve, astfel încât puteţi avea o configurare asincronă, de asemenea.

Dacă doriţi să rulaţi ceva logică înaintea fiecărui test, nu înainte de toate testele, se poate utiliza beforeEach în schimb.

Dacă doriţi să rulaţi ceva logică înaintea fiecărui test, nu înainte de toate testele, se poate utiliza beforeEach în schimb.

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.

De exemplu:

De exemplu:

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();
});
});

În cazul în care beforeEach este în interiorul unui bloc describe, se va executa înainte de fiecare test din interiorul blocului.

Dacă aveţi nevoie doar să rulați ceva cod de configurare o singură dată, înainte de orice test, utilizaţi beforeAll.

Dacă aveţi nevoie doar să rulați ceva cod de configurare o singură dată, înainte de orice test, utilizaţi beforeAll.

describe(name, fn)#

describe(name, fn) creates a block that groups together several related tests. De exemplu, dacă aveţi un obiect myBeverage, care se presupune a fi delicios, dar nu acru, aţi putea test acest lucru în felul următor:

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.

Puteţi, de asemenea, imbrica blocuri describe în cazul în care aveţi o ierarhie de teste:

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]]
  • 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 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.

Example:

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 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.

Example:

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)#

Aveţi posibilitatea să utilizaţi describe.only dacă doriţi să se execute un singur bloc describe:

Aveţi posibilitatea să utilizaţi describe.only dacă doriţi să se execute un singur bloc 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)#

Aveţi posibilitatea să utilizaţi describe.skip dacă nu doriţi să se execute un anumit bloc describe:

Aveţi posibilitatea să utilizaţi describe.skip dacă nu doriţi să se execute un anumit bloc 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)

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

Primul argument este numele testului; al doilea argument este o funcţie care conţine aserțiunile pentru test. The third argument (optional) is timeout (in milliseconds) for specifying how long to wait before aborting. Note: The default timeout is 5 seconds.

Notă: În cazul în care o promisiune este returnată din test, Jest va aştepta rezolvarea promisiunii înainte ca testul să se finalizeze. Jest va aştepta, de asemenea, și dacă pasați un argument la funcţia de test, numit de obicei done. Acest lucru ar putea fi util atunci când testați callback-uri. Aflaţi cum să testați cod asincron aici.

For example, let's say fetchBeverageList() returns a promise that is supposed to resolve to a list that has lemon in it. Puteți testa acest lucru în felul următor:

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

Chiar dacă apelul pentru test va returna imediat, testul nu se va finaliza doar după rezolvarea promisiunii.

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]]
  • 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 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.

Example:

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 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.

Example:

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.

De exemplu, să presupunem că aveți aceste teste:

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)

Atunci când lucrați cu baze mari de cod, puteţi găsi, uneori, un test care este temporar stricat din diverse motive. 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.

De exemplu, să presupunem că aveți aceste teste:

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

Doar testul "it is raining" va rula, deoarece celălalt test este apelat cu 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.

Example:

const add = (a, b) => a + b;
test.todo('add should be associative');