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Bun

module

bun:test

The 'bun:test' module is a fast, built-in test runner that aims for Jest compatibility. Tests are executed with the Bun runtime, providing significantly improved performance over traditional test runners.

Key features include TypeScript and JSX support, lifecycle hooks (beforeAll, beforeEach, afterEach, afterAll), snapshot testing, UI & DOM testing, watch mode, and script pre-loading. The API supports test assertions with expect, test grouping with describe, mocks, and more.

While Bun aims for compatibility with Jest, not everything is implemented yet. Use bun test to automatically discover and run tests matching common patterns like *.test.ts or *.spec.js.

  • Describes a group of related tests.

    function sum(a, b) {
  return a + b;
}
describe("sum()", () => {
  test("can sum two values", () => {
    expect(sum(1, 1)).toBe(2);
  });
});
  • const expect: Expect

    Asserts that a value matches some criteria.

    expect(1 + 1).toBe(2);
expect([1,2,3]).toContain(2);
expect(null).toBeNull();
  • const jest: Jest
  • const mock: (Function?: T) => Mock<T>
  • const test: Test

    Runs a test.

    test("can check if using Bun", () => {
  expect(Bun).toBeDefined();
});

test("can make a fetch() request", async () => {
  const response = await fetch("https://example.com/");
  expect(response.ok).toBe(true);
});
  • function afterAll(
    fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void
    ): void;

    Runs a function, once, after all the tests.

    This is useful for running clean up tasks, like closing a socket or deleting temporary files.

    @param fn

    the function to run

    let database;
afterAll(async () => {
  if (database) {
    await database.close();
  }
});
  • function afterEach(
    fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void
    ): void;

    Runs a function after each test.

    This is useful for running clean up tasks, like closing a socket or deleting temporary files.

    @param fn

    the function to run

  • function beforeAll(
    fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void
    ): void;

    Runs a function, once, before all the tests.

    This is useful for running set up tasks, like initializing a global variable or connecting to a database.

    If this function throws, tests will not run in this file.

    @param fn

    the function to run

    let database;
beforeAll(async () => {
  database = await connect("localhost");
});
  • function beforeEach(
    fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void
    ): void;

    Runs a function before each test.

    This is useful for running set up tasks, like initializing a global variable or connecting to a database.

    If this function throws, the test will not run.

    @param fn

    the function to run

  • milliseconds: number
    ): void;

    Sets the default timeout for all tests in the current file. If a test specifies a timeout, it will override this value. The default timeout is 5000ms (5 seconds).

    @param milliseconds

    the number of milliseconds for the default timeout

  • function setSystemTime(
    now?: number | Date
    ): ThisType<void>;

    Control the system time used by:

    • Date.now()
    • new Date()
    • Intl.DateTimeFormat().format()

    In the future, we may add support for more functions, but we haven't done that yet.

    @param now

    The time to set the system time to. If not provided, the system time will be reset.

    @returns

    this

  • function spyOn<T extends object, K extends string | number | symbol>(
    obj: T,
    methodOrPropertyValue: K
    ): Mock<Extract<T[K], (...args: any[]) => any>>;

Type definitions

  • namespace jest

    • type Mock<T extends (...args: any[]) => any = (...args: any[]) => any> = JestMock.Mock<T>

      Constructs the type of a mock function, e.g. the return type of jest.fn().

    • type Replaced<T> = JestMock.Replaced<T>

      Constructs the type of a replaced property.

    • type Spied<T extends JestMock.ClassLike | (...args: any[]) => any> = JestMock.Spied<T>

      Constructs the type of a spied class or function.

    • type SpiedClass<T extends JestMock.ClassLike> = JestMock.SpiedClass<T>

      Constructs the type of a spied class.

    • type SpiedFunction<T extends (...args: any[]) => any> = JestMock.SpiedFunction<T>

      Constructs the type of a spied function.

    • type SpiedGetter<T> = JestMock.SpiedGetter<T>

      Constructs the type of a spied getter.

    • type SpiedSetter<T> = JestMock.SpiedSetter<T>

      Constructs the type of a spied setter.

  • interface AsymmetricMatchers

    You can extend this interface with declaration merging, in order to add type support for custom asymmetric matchers.

    // my_modules.d.ts
interface MyCustomMatchers {
  toBeWithinRange(floor: number, ceiling: number): any;
}
declare module "bun:test" {
  interface Matchers<T> extends MyCustomMatchers {}
  interface AsymmetricMatchers extends MyCustomMatchers {}
}
    • constructor: (...args: any[]) => any | new (...args: any[]) => any
      ): any;

      Matches anything that was created with the given constructor. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      function randocall(fn) {
  return fn(Math.floor(Math.random() * 6 + 1));
}

test('randocall calls its callback with a number', () => {
  const mock = jest.fn();
  randocall(mock);
  expect(mock).toBeCalledWith(expect.any(Number));
});
    • anything(): any;

      Matches anything but null or undefined. You can use it inside toEqual or toBeCalledWith instead of a literal value. For example, if you want to check that a mock function is called with a non-null argument:

      test('map calls its argument with a non-null argument', () => {
  const mock = jest.fn();
  [1].map(x => mock(x));
  expect(mock).toBeCalledWith(expect.anything());
});
    • arrayContaining<E = any>(
      arr: readonly E[]
      ): any;

      Matches any array made up entirely of elements in the provided array. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      Optionally, you can provide a type for the elements via a generic.

    • num: number,
      numDigits?: number
      ): any;

      Useful when comparing floating point numbers in object properties or array item. If you need to compare a number, use .toBeCloseTo instead.

      The optional numDigits argument limits the number of digits to check after the decimal point. For the default value 2, the test criterion is Math.abs(expected - received) < 0.005 (that is, 10 ** -2 / 2).

    • obj: object
      ): any;

      Matches any object that recursively matches the provided keys. This is often handy in conjunction with other asymmetric matchers.

      Optionally, you can provide a type for the object via a generic. This ensures that the object contains the desired structure.

    • str: string | String
      ): any;

      Matches any received string that contains the exact expected string

    • regex: string | String | RegExp
      ): any;

      Matches any string that contains the exact provided string

  • interface AsymmetricMatchersBuiltin

    • constructor: (...args: any[]) => any | new (...args: any[]) => any
      ): any;

      Matches anything that was created with the given constructor. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      function randocall(fn) {
  return fn(Math.floor(Math.random() * 6 + 1));
}

test('randocall calls its callback with a number', () => {
  const mock = jest.fn();
  randocall(mock);
  expect(mock).toBeCalledWith(expect.any(Number));
});
    • anything(): any;

      Matches anything but null or undefined. You can use it inside toEqual or toBeCalledWith instead of a literal value. For example, if you want to check that a mock function is called with a non-null argument:

      test('map calls its argument with a non-null argument', () => {
  const mock = jest.fn();
  [1].map(x => mock(x));
  expect(mock).toBeCalledWith(expect.anything());
});
    • arrayContaining<E = any>(
      arr: readonly E[]
      ): any;

      Matches any array made up entirely of elements in the provided array. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      Optionally, you can provide a type for the elements via a generic.

    • num: number,
      numDigits?: number
      ): any;

      Useful when comparing floating point numbers in object properties or array item. If you need to compare a number, use .toBeCloseTo instead.

      The optional numDigits argument limits the number of digits to check after the decimal point. For the default value 2, the test criterion is Math.abs(expected - received) < 0.005 (that is, 10 ** -2 / 2).

    • obj: object
      ): any;

      Matches any object that recursively matches the provided keys. This is often handy in conjunction with other asymmetric matchers.

      Optionally, you can provide a type for the object via a generic. This ensures that the object contains the desired structure.

    • str: string | String
      ): any;

      Matches any received string that contains the exact expected string

    • regex: string | String | RegExp
      ): any;

      Matches any string that contains the exact provided string

  • interface Describe

    Describes a group of related tests.

    function sum(a, b) {
  return a + b;
}
describe("sum()", () => {
  test("can sum two values", () => {
    expect(sum(1, 1)).toBe(2);
  });
});
    • each<T extends readonly [any, any]>(
      table: readonly T[]
      ): (label: DescribeLabel, fn: (...args: [...T[]]) => void | Promise<unknown>, options?: number | TestOptions) => void;

      Returns a function that runs for each item in table.

      @param table

      Array of Arrays with the arguments that are passed into the test fn for each row.

      each<T extends any[]>(
      table: readonly T[]
      ): (label: DescribeLabel, fn: (...args: Readonly<T>) => void | Promise<unknown>, options?: number | TestOptions) => void;
      each<T>(
      table: T[]
      ): (label: DescribeLabel, fn: (...args: T[]) => void | Promise<unknown>, options?: number | TestOptions) => void;
    • condition: boolean
      ): (label: DescribeLabel, fn: () => void) => void;

      Runs this group of tests, only if condition is true.

      This is the opposite of describe.skipIf().

      @param condition

      if these tests should run

    • label: DescribeLabel,
      fn: () => void
      ): void;

      Skips all other tests, except this group of tests.

      @param label

      the label for the tests

      @param fn

      the function that defines the tests

    • label: DescribeLabel,
      fn: () => void
      ): void;

      Skips this group of tests.

      @param label

      the label for the tests

      @param fn

      the function that defines the tests

    • condition: boolean
      ): (label: DescribeLabel, fn: () => void) => void;

      Skips this group of tests, if condition is true.

      @param condition

      if these tests should be skipped

    • label: DescribeLabel,
      fn?: () => void
      ): void;

      Marks this group of tests as to be written or to be fixed.

      @param label

      the label for the tests

      @param fn

      the function that defines the tests

    • condition: boolean
      ): (label: DescribeLabel, fn: () => void) => void;

      Marks this group of tests as to be written or to be fixed, if condition is true.

      @param condition

      if these tests should be skipped

  • interface Expect

    You can extend this interface with declaration merging, in order to add type support for custom asymmetric matchers.

    // my_modules.d.ts
interface MyCustomMatchers {
  toBeWithinRange(floor: number, ceiling: number): any;
}
declare module "bun:test" {
  interface Matchers<T> extends MyCustomMatchers {}
  interface AsymmetricMatchers extends MyCustomMatchers {}
}
    • not: ExpectNot

      Access to negated asymmetric matchers.

      expect("abc").toEqual(expect.stringContaining("abc")); // will pass
expect("abc").toEqual(expect.not.stringContaining("abc")); // will fail
    • rejectsTo: AsymmetricMatchers

      Create an asymmetric matcher for a promise rejected value.

      expect(Promise.reject("error")).toEqual(expect.rejectsTo.stringContaining("error")); // will pass
expect(Promise.resolve("error")).toEqual(expect.rejectsTo.stringContaining("error")); // will fail
expect("error").toEqual(expect.rejectsTo.stringContaining("error")); // will fail
    • resolvesTo: AsymmetricMatchers

      Create an asymmetric matcher for a promise resolved value.

      expect(Promise.resolve("value")).toEqual(expect.resolvesTo.stringContaining("value")); // will pass
expect(Promise.reject("value")).toEqual(expect.resolvesTo.stringContaining("value")); // will fail
expect("value").toEqual(expect.resolvesTo.stringContaining("value")); // will fail
    • constructor: (...args: any[]) => any | new (...args: any[]) => any
      ): any;

      Matches anything that was created with the given constructor. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      function randocall(fn) {
  return fn(Math.floor(Math.random() * 6 + 1));
}

test('randocall calls its callback with a number', () => {
  const mock = jest.fn();
  randocall(mock);
  expect(mock).toBeCalledWith(expect.any(Number));
});
    • anything(): any;

      Matches anything but null or undefined. You can use it inside toEqual or toBeCalledWith instead of a literal value. For example, if you want to check that a mock function is called with a non-null argument:

      test('map calls its argument with a non-null argument', () => {
  const mock = jest.fn();
  [1].map(x => mock(x));
  expect(mock).toBeCalledWith(expect.anything());
});
    • arrayContaining<E = any>(
      arr: readonly E[]
      ): any;

      Matches any array made up entirely of elements in the provided array. You can use it inside toEqual or toBeCalledWith instead of a literal value.

      Optionally, you can provide a type for the elements via a generic.

    • neededAssertions: number
      ): void;

      Ensures that a specific number of assertions are made

    • num: number,
      numDigits?: number
      ): any;

      Useful when comparing floating point numbers in object properties or array item. If you need to compare a number, use .toBeCloseTo instead.

      The optional numDigits argument limits the number of digits to check after the decimal point. For the default value 2, the test criterion is Math.abs(expected - received) < 0.005 (that is, 10 ** -2 / 2).

    • extend<M>(
      matchers: ExpectExtendMatchers<M>
      ): void;

      Register new custom matchers.

      @param matchers

      An object containing the matchers to register, where each key is the matcher name, and its value the implementation function. The function must satisfy: (actualValue, ...matcherInstantiationArguments) => { pass: true|false, message: () => string }

      expect.extend({
    toBeWithinRange(actual, min, max) {
        if (typeof actual !== 'number' || typeof min !== 'number' || typeof max !== 'number')
            throw new Error('Invalid usage');
        const pass = actual >= min && actual <= max;
        return {
            pass: pass,
            message: () => `expected ${this.utils.printReceived(actual)} ` +
                (pass ? `not to be`: `to be`) + ` within range ${this.utils.printExpected(`${min} .. ${max}`)}`,
        };
    },
});

test('some test', () => {
  expect(50).toBeWithinRange(0, 100); // will pass
  expect(50).toBeWithinRange(100, 200); // will fail
  expect(50).toBe(expect.toBeWithinRange(0, 100)); // will pass
  expect(50).toBe(expect.not.toBeWithinRange(100, 200)); // will pass
});
    • hasAssertions(): void;

      Ensures that an assertion is made

    • obj: object
      ): any;

      Matches any object that recursively matches the provided keys. This is often handy in conjunction with other asymmetric matchers.

      Optionally, you can provide a type for the object via a generic. This ensures that the object contains the desired structure.

    • str: string | String
      ): any;

      Matches any received string that contains the exact expected string

    • regex: string | String | RegExp
      ): any;

      Matches any string that contains the exact provided string

    • msg?: string | Error
      ): never;

      Throw an error if this function is called.

      @param msg

      Optional message to display if the test fails

      @returns

      never

      import { expect, test } from "bun:test";

test("!!abc!! is not a module", () => {
 try {
    require("!!abc!!");
    expect.unreachable();
 } catch(e) {
    expect(e.name).not.toBe("UnreachableError");
 }
});

  • interface MatcherResult

  • interface Matchers<T = unknown>

    You can extend this interface with declaration merging, in order to add type support for custom matchers.

    // my_modules.d.ts
interface MyCustomMatchers {
  toBeWithinRange(floor: number, ceiling: number): any;
}
declare module "bun:test" {
  interface Matchers<T> extends MyCustomMatchers {}
  interface AsymmetricMatchers extends MyCustomMatchers {}
}
    • fail: (message?: string) => void

      Assertion which fails.

      expect().fail();
expect().fail("message is optional");
expect().not.fail();
expect().not.fail("hi");
    • not: Matchers<unknown>

      Negates the result of a subsequent assertion. If you know how to test something, .not lets you test its opposite.

      expect(1).not.toBe(0);
expect(null).not.toBeNull();
    • pass: (message?: string) => void

      Assertion which passes.

      expect().pass();
expect().pass("message is optional");
expect().not.pass();
expect().not.pass("hi");
    • rejects: Matchers<unknown>

      Expects the value to be a promise that rejects.

      expect(Promise.reject("error")).rejects.toBe("error");
    • resolves: Matchers<Awaited<T>>

      Expects the value to be a promise that resolves.

      expect(Promise.resolve(1)).resolves.toBe(1);
    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • n: number,
      ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • expected: T
      ): void;

      Asserts that a value equals what is expected.

      • For non-primitive values, like objects and arrays, use toEqual() instead.
      • For floating-point numbers, use toBeCloseTo() instead.
      @param expected

      the expected value

      expect(100 + 23).toBe(123);
expect("d" + "og").toBe("dog");
expect([123]).toBe([123]); // fail, use toEqual()
expect(3 + 0.14).toBe(3.14); // fail, use toBeCloseTo()
    • toBeArray(): void;

      Asserts that a value is a array.

      expect([1]).toBeArray();
expect(new Array(1)).toBeArray();
expect({}).not.toBeArray();
    • size: number
      ): void;

      Asserts that a value is a array of a certain length.

      expect([]).toBeArrayOfSize(0);
expect([1]).toBeArrayOfSize(1);
expect(new Array(1)).toBeArrayOfSize(1);
expect({}).not.toBeArrayOfSize(0);
    • toBeBoolean(): void;

      Asserts that a value is a boolean.

      expect(true).toBeBoolean();
expect(false).toBeBoolean();
expect(null).not.toBeBoolean();
expect(0).not.toBeBoolean();
    • toBeCalled(): void;

      Ensures that a mock function is called an exact number of times.

    • expected: number
      ): void;

      Ensure that a mock function is called with specific arguments.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments.

    • expected: number,
      numDigits?: number
      ): void;

      Asserts that value is close to the expected by floating point precision.

      For example, the following fails because arithmetic on decimal (base 10) values often have rounding errors in limited precision binary (base 2) representation.

      @param expected

      the expected value

      @param numDigits

      the number of digits to check after the decimal point. Default is 2

      expect(0.2 + 0.1).toBe(0.3); // fails

Use `toBeCloseTo` to compare floating point numbers for approximate equality.
    • toBeDate(): void;

      Asserts that a value is a Date object.

      To check if a date is valid, use toBeValidDate() instead.

      expect(new Date()).toBeDate();
expect(new Date(null)).toBeDate();
expect("2020-03-01").not.toBeDate();
    • toBeDefined(): void;

      Asserts that a value is defined. (e.g. is not undefined)

      expect(true).toBeDefined();
expect(undefined).toBeDefined(); // fail
    • toBeEmpty(): void;

      Asserts that a value is empty.

      expect("").toBeEmpty();
expect([]).toBeEmpty();
expect({}).toBeEmpty();
expect(new Set()).toBeEmpty();

    • Asserts that a value is an empty object.

      expect({}).toBeEmptyObject();
expect({ a: 'hello' }).not.toBeEmptyObject();
    • toBeEven(): void;

      Asserts that a number is even.

      expect(2).toBeEven();
expect(1).not.toBeEven();
    • toBeFalse(): void;

      Asserts that a value is false.

      expect(false).toBeFalse();
expect(true).not.toBeFalse();
expect(0).not.toBeFalse();
    • toBeFalsy(): void;

      Asserts that a value is "falsy".

      To assert that a value equals false, use toBe(false) instead.

      expect(true).toBeTruthy();
expect(1).toBeTruthy();
expect({}).toBeTruthy();
    • toBeFinite(): void;

      Asserts that a value is a number, and is not NaN or Infinity.

      expect(1).toBeFinite();
expect(3.14).toBeFinite();
expect(NaN).not.toBeFinite();
expect(Infinity).not.toBeFinite();
    • toBeFunction(): void;

      Asserts that a value is a function.

      expect(() => {}).toBeFunction();
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is greater than the expected value.

      @param expected

      the expected number

      expect(1).toBeGreaterThan(0);
expect(3.14).toBeGreaterThan(3);
expect(9).toBeGreaterThan(9); // fail
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is greater than or equal to the expected value.

      @param expected

      the expected number

      expect(1).toBeGreaterThanOrEqual(0);
expect(3.14).toBeGreaterThanOrEqual(3);
expect(9).toBeGreaterThanOrEqual(9);
    • value: unknown
      ): void;

      Asserts that the expected value is an instance of value

      expect([]).toBeInstanceOf(Array);
expect(null).toBeInstanceOf(Array); // fail
    • toBeInteger(): void;

      Asserts that a value is a number, and is an integer.

      expect(1).toBeInteger();
expect(3.14).not.toBeInteger();
expect(NaN).not.toBeInteger();
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is less than the expected value.

      @param expected

      the expected number

      expect(-1).toBeLessThan(0);
expect(3).toBeLessThan(3.14);
expect(9).toBeLessThan(9); // fail
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is less than or equal to the expected value.

      @param expected

      the expected number

      expect(-1).toBeLessThanOrEqual(0);
expect(3).toBeLessThanOrEqual(3.14);
expect(9).toBeLessThanOrEqual(9);
    • toBeNaN(): void;

      Asserts that a value is NaN.

      Same as using Number.isNaN().

      expect(NaN).toBeNaN();
expect(Infinity).toBeNaN(); // fail
expect("notanumber").toBeNaN(); // fail
    • toBeNegative(): void;

      Asserts that a value is a negative number.

      expect(-3.14).toBeNegative();
expect(1).not.toBeNegative();
expect(NaN).not.toBeNegative();
    • toBeNil(): void;

      Asserts that a value is null or undefined.

      expect(null).toBeNil();
expect(undefined).toBeNil();
    • toBeNull(): void;

      Asserts that a value is null.

      expect(null).toBeNull();
expect(undefined).toBeNull(); // fail
    • toBeNumber(): void;

      Asserts that a value is a number.

      expect(1).toBeNumber();
expect(3.14).toBeNumber();
expect(NaN).toBeNumber();
expect(BigInt(1)).not.toBeNumber();
    • toBeObject(): void;

      Asserts that a value is an object.

      expect({}).toBeObject();
expect("notAnObject").not.toBeObject();
expect(NaN).not.toBeObject();
    • toBeOdd(): void;

      Asserts that a number is odd.

      expect(1).toBeOdd();
expect(2).not.toBeOdd();
    • expected: unknown[] | Iterable<unknown, any, any>
      ): void;

      Asserts that the value is deep equal to an element in the expected array.

      The value must be an array or iterable, which includes strings.

      @param expected

      the expected value

      expect(1).toBeOneOf([1,2,3]);
expect("foo").toBeOneOf(["foo", "bar"]);
expect(true).toBeOneOf(new Set([true]));
    • toBePositive(): void;

      Asserts that a value is a positive number.

      expect(1).toBePositive();
expect(-3.14).not.toBePositive();
expect(NaN).not.toBePositive();
    • toBeString(): void;

      Asserts that a value is a string.

      expect("foo").toBeString();
expect(new String("bar")).toBeString();
expect(123).not.toBeString();
    • toBeSymbol(): void;

      Asserts that a value is a symbol.

      expect(Symbol("foo")).toBeSymbol();
expect("foo").not.toBeSymbol();
    • toBeTrue(): void;

      Asserts that a value is true.

      expect(true).toBeTrue();
expect(false).not.toBeTrue();
expect(1).not.toBeTrue();
    • toBeTruthy(): void;

      Asserts that a value is "truthy".

      To assert that a value equals true, use toBe(true) instead.

      expect(true).toBeTruthy();
expect(1).toBeTruthy();
expect({}).toBeTruthy();
    • type: 'string' | 'number' | 'bigint' | 'boolean' | 'symbol' | 'undefined' | 'object' | 'function'
      ): void;

      Asserts that a value matches a specific type.

      expect(1).toBeTypeOf("number");
expect("hello").toBeTypeOf("string");
expect([]).not.toBeTypeOf("boolean");
    • toBeUndefined(): void;

      Asserts that a value is undefined.

      expect(undefined).toBeUndefined();
expect(null).toBeUndefined(); // fail
    • toBeValidDate(): void;

      Asserts that a value is a valid Date object.

      expect(new Date()).toBeValidDate();
expect(new Date(null)).not.toBeValidDate();
expect("2020-03-01").not.toBeValidDate();
    • start: number,
      end: number
      ): void;

      Asserts that a value is a number between a start and end value.

      @param start

      the start number (inclusive)

      @param end

      the end number (exclusive)

    • expected: unknown
      ): void;

      Asserts that a value contains what is expected.

      The value must be an array or iterable, which includes strings.

      @param expected

      the expected value

      expect([1, 2, 3]).toContain(1);
expect(new Set([true])).toContain(true);
expect("hello").toContain("o");
    • expected: unknown
      ): void;

      Asserts that an object contains all the provided keys.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'hello', b: 'world' }).toContainAllKeys(['a','b']);
expect({ a: 'hello', b: 'world' }).toContainAllKeys(['b','a']);
expect({ 1: 'hello', b: 'world' }).toContainAllKeys([1,'b']);
expect({ a: 'hello', b: 'world' }).not.toContainAllKeys(['c']);
expect({ a: 'hello', b: 'world' }).not.toContainAllKeys(['a']);
    • expected: unknown
      ): void;

      Asserts that an object contain all the provided values.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainAllValues(['foo', 'bar', 'baz']);
expect(o).toContainAllValues(['baz', 'bar', 'foo']);
expect(o).not.toContainAllValues(['bar', 'foo']);
    • expected: unknown
      ): void;

      Asserts that an object contains at least one of the provided keys. Asserts that an object contains all the provided keys.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['a']);
expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['b']);
expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['b', 'c']);
expect({ a: 'hello', b: 'world' }).not.toContainAnyKeys(['c']);
    • expected: unknown
      ): void;

      Asserts that an object contain any provided value.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainAnyValues(['qux', 'foo']);
expect(o).toContainAnyValues(['qux', 'bar']);
expect(o).toContainAnyValues(['qux', 'baz']);
expect(o).not.toContainAnyValues(['qux']);
    • expected: unknown
      ): void;

      Asserts that a value contains and equals what is expected.

      This matcher will perform a deep equality check for members of arrays, rather than checking for object identity.

      @param expected

      the expected value

      expect([{ a: 1 }]).toContainEqual({ a: 1 });
expect([{ a: 1 }]).not.toContainEqual({ a: 2 });
    • expected: unknown
      ): void;

      Asserts that an object contains a key.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('a');
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('b');
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('c');
expect({ a: 'foo', b: 'bar', c: 'baz' }).not.toContainKey('d');
    • expected: unknown
      ): void;

      Asserts that an object contains all the provided keys.

      @param expected

      the expected value

      expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKeys(['a', 'b']);
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKeys(['a', 'b', 'c']);
expect({ a: 'foo', b: 'bar', c: 'baz' }).not.toContainKeys(['a', 'b', 'e']);
    • expected: unknown
      ): void;

      Asserts that an object contain the provided value.

      The value must be an object

      @param expected

      the expected value

      const shallow = { hello: "world" };
const deep = { message: shallow };
const deepArray = { message: [shallow] };
const o = { a: "foo", b: [1, "hello", true], c: "baz" };

expect(shallow).toContainValue("world");
expect({ foo: false }).toContainValue(false);
expect(deep).toContainValue({ hello: "world" });
expect(deepArray).toContainValue([{ hello: "world" }]);

expect(o).toContainValue("foo", "barr");
expect(o).toContainValue([1, "hello", true]);
expect(o).not.toContainValue("qux");

// NOT
expect(shallow).not.toContainValue("foo");
expect(deep).not.toContainValue({ foo: "bar" });
expect(deepArray).not.toContainValue([{ foo: "bar" }]);
    • expected: unknown
      ): void;

      Asserts that an object contain the provided value.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainValues(['foo']);
expect(o).toContainValues(['baz', 'bar']);
expect(o).not.toContainValues(['qux', 'foo']);
    • expected: string
      ): void;

      Asserts that a value ends with a string.

      @param expected

      the string to end with

    • expected: T
      ): void;

      Asserts that a value is deeply equal to what is expected.

      @param expected

      the expected value

      expect(100 + 23).toBe(123);
expect("d" + "og").toBe("dog");
expect([456]).toEqual([456]);
expect({ value: 1 }).toEqual({ value: 1 });
    • expected: string
      ): void;

      Asserts that a value is equal to the expected string, ignoring any whitespace.

      @param expected

      the expected string

      expect(" foo ").toEqualIgnoringWhitespace("foo");
expect("bar").toEqualIgnoringWhitespace(" bar ");

    • Ensures that a mock function is called.

    • expected: number
      ): void;

      Ensures that a mock function is called an exact number of times.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the last call.

    • n: number,
      ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • length: number
      ): void;

      Asserts that a value has a .length property that is equal to the expected length.

      @param length

      the expected length

      expect([]).toHaveLength(0);
expect("hello").toHaveLength(4);
    • keyPath: string | number | string | number[],
      value?: unknown
      ): void;

      Asserts that a value has a property with the expected name, and value if provided.

      @param keyPath

      the expected property name or path, or an index

      @param value

      the expected property value, if provided

      expect(new Set()).toHaveProperty("size");
expect(new Uint8Array()).toHaveProperty("byteLength", 0);
expect({ kitchen: { area: 20 }}).toHaveProperty("kitchen.area", 20);
expect({ kitchen: { area: 20 }}).toHaveProperty(["kitchen", "area"], 20);

    • Ensures that a mock function has returned successfully at least once.

      A promise that is unfulfilled will be considered a failure. If the function threw an error, it will be considered a failure.

    • times: number
      ): void;

      Ensures that a mock function has returned successfully at times times.

      A promise that is unfulfilled will be considered a failure. If the function threw an error, it will be considered a failure.

    • expected: string
      ): void;

      Asserts that a value includes a string.

      For non-string values, use toContain() instead.

      @param expected

      the expected substring

    • expected: string,
      times: number
      ): void;

      Asserts that a value includes a string {times} times.

      @param expected

      the expected substring

      @param times

      the number of times the substring should occur

    • expected: string | RegExp
      ): void;

      Asserts that a value matches a regular expression or includes a substring.

      @param expected

      the expected substring or pattern.

      expect("dog").toMatch(/dog/);
expect("dog").toMatch("og");
    • value?: string
      ): void;

      Asserts that a value matches the most recent inline snapshot.

      @param value

      The latest automatically-updated snapshot value.

      expect("Hello").toMatchInlineSnapshot();
expect("Hello").toMatchInlineSnapshot(`"Hello"`);
      propertyMatchers?: object,
      value?: string
      ): void;

      Asserts that a value matches the most recent inline snapshot.

      @param propertyMatchers

      Object containing properties to match against the value.

      @param value

      The latest automatically-updated snapshot value.

      expect({ c: new Date() }).toMatchInlineSnapshot({ c: expect.any(Date) });
expect({ c: new Date() }).toMatchInlineSnapshot({ c: expect.any(Date) }, `
{
  "v": Any<Date>,
}
`);
    • subset: object
      ): void;

      Asserts that an object matches a subset of properties.

      @param subset

      Subset of properties to match with.

      expect({ a: 1, b: 2 }).toMatchObject({ b: 2 });
expect({ c: new Date(), d: 2 }).toMatchObject({ d: 2 });
    • hint?: string
      ): void;

      Asserts that a value matches the most recent snapshot.

      @param hint

      Hint used to identify the snapshot in the snapshot file.

      expect([1, 2, 3]).toMatchSnapshot('hint message');
      propertyMatchers?: object,
      hint?: string
      ): void;

      Asserts that a value matches the most recent snapshot.

      @param propertyMatchers

      Object containing properties to match against the value.

      @param hint

      Hint used to identify the snapshot in the snapshot file.

      expect([1, 2, 3]).toMatchSnapshot();
expect({ a: 1, b: 2 }).toMatchSnapshot({ a: 1 });
expect({ c: new Date() }).toMatchSnapshot({ c: expect.any(Date) });
    • predicate: (value: T) => boolean
      ): void;

      Checks whether a value satisfies a custom condition.

      @param predicate

      The custom condition to be satisfied. It should be a function that takes a value as an argument (in this case the value from expect) and returns a boolean.

      expect(1).toSatisfy((val) => val > 0);
expect("foo").toSatisfy((val) => val === "foo");
expect("bar").not.toSatisfy((val) => val === "bun");
    • expected: string
      ): void;

      Asserts that a value starts with a string.

      @param expected

      the string to start with

    • expected: T
      ): void;

      Asserts that a value is deeply and strictly equal to what is expected.

      There are two key differences from toEqual():

      1. It checks that the class is the same.
      2. It checks that undefined values match as well.
      @param expected

      the expected value

      class Dog {
  type = "dog";
}
const actual = new Dog();
expect(actual).toStrictEqual(new Dog());
expect(actual).toStrictEqual({ type: "dog" }); // fail
    • expected?: unknown
      ): void;

      Asserts that a function throws an error.

      • If expected is a string or RegExp, it will check the message property.
      • If expected is an Error object, it will check the name and message properties.
      • If expected is an Error constructor, it will check the class of the Error.
      • If expected is not provided, it will check if anything has thrown.
      @param expected

      the expected error, error message, or error pattern

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrow("Oops!");
expect(fail).toThrow(/oops/i);
expect(fail).toThrow(Error);
expect(fail).toThrow();
    • expected?: unknown
      ): void;

      Asserts that a function throws an error.

      • If expected is a string or RegExp, it will check the message property.
      • If expected is an Error object, it will check the name and message properties.
      • If expected is an Error constructor, it will check the class of the Error.
      • If expected is not provided, it will check if anything has thrown.
      @param expected

      the expected error, error message, or error pattern

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowError("Oops!");
expect(fail).toThrowError(/oops/i);
expect(fail).toThrowError(Error);
expect(fail).toThrowError();
    • value?: string
      ): void;

      Asserts that a function throws an error matching the most recent snapshot.

      @param value

      The latest automatically-updated snapshot value.

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowErrorMatchingInlineSnapshot();
expect(fail).toThrowErrorMatchingInlineSnapshot(`"Oops!"`);
    • hint?: string
      ): void;

      Asserts that a function throws an error matching the most recent snapshot.

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowErrorMatchingSnapshot();
expect(fail).toThrowErrorMatchingSnapshot("This one should say Oops!");

  • interface MatchersBuiltin<T = unknown>

    • fail: (message?: string) => void

      Assertion which fails.

      expect().fail();
expect().fail("message is optional");
expect().not.fail();
expect().not.fail("hi");
    • not: Matchers<unknown>

      Negates the result of a subsequent assertion. If you know how to test something, .not lets you test its opposite.

      expect(1).not.toBe(0);
expect(null).not.toBeNull();
    • pass: (message?: string) => void

      Assertion which passes.

      expect().pass();
expect().pass("message is optional");
expect().not.pass();
expect().not.pass("hi");
    • rejects: Matchers<unknown>

      Expects the value to be a promise that rejects.

      expect(Promise.reject("error")).rejects.toBe("error");
    • resolves: Matchers<Awaited<T>>

      Expects the value to be a promise that resolves.

      expect(Promise.resolve(1)).resolves.toBe(1);
    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • n: number,
      ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • expected: T
      ): void;

      Asserts that a value equals what is expected.

      • For non-primitive values, like objects and arrays, use toEqual() instead.
      • For floating-point numbers, use toBeCloseTo() instead.
      @param expected

      the expected value

      expect(100 + 23).toBe(123);
expect("d" + "og").toBe("dog");
expect([123]).toBe([123]); // fail, use toEqual()
expect(3 + 0.14).toBe(3.14); // fail, use toBeCloseTo()
    • toBeArray(): void;

      Asserts that a value is a array.

      expect([1]).toBeArray();
expect(new Array(1)).toBeArray();
expect({}).not.toBeArray();
    • size: number
      ): void;

      Asserts that a value is a array of a certain length.

      expect([]).toBeArrayOfSize(0);
expect([1]).toBeArrayOfSize(1);
expect(new Array(1)).toBeArrayOfSize(1);
expect({}).not.toBeArrayOfSize(0);
    • toBeBoolean(): void;

      Asserts that a value is a boolean.

      expect(true).toBeBoolean();
expect(false).toBeBoolean();
expect(null).not.toBeBoolean();
expect(0).not.toBeBoolean();
    • toBeCalled(): void;

      Ensures that a mock function is called an exact number of times.

    • expected: number
      ): void;

      Ensure that a mock function is called with specific arguments.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments.

    • expected: number,
      numDigits?: number
      ): void;

      Asserts that value is close to the expected by floating point precision.

      For example, the following fails because arithmetic on decimal (base 10) values often have rounding errors in limited precision binary (base 2) representation.

      @param expected

      the expected value

      @param numDigits

      the number of digits to check after the decimal point. Default is 2

      expect(0.2 + 0.1).toBe(0.3); // fails

Use `toBeCloseTo` to compare floating point numbers for approximate equality.
    • toBeDate(): void;

      Asserts that a value is a Date object.

      To check if a date is valid, use toBeValidDate() instead.

      expect(new Date()).toBeDate();
expect(new Date(null)).toBeDate();
expect("2020-03-01").not.toBeDate();
    • toBeDefined(): void;

      Asserts that a value is defined. (e.g. is not undefined)

      expect(true).toBeDefined();
expect(undefined).toBeDefined(); // fail
    • toBeEmpty(): void;

      Asserts that a value is empty.

      expect("").toBeEmpty();
expect([]).toBeEmpty();
expect({}).toBeEmpty();
expect(new Set()).toBeEmpty();

    • Asserts that a value is an empty object.

      expect({}).toBeEmptyObject();
expect({ a: 'hello' }).not.toBeEmptyObject();
    • toBeEven(): void;

      Asserts that a number is even.

      expect(2).toBeEven();
expect(1).not.toBeEven();
    • toBeFalse(): void;

      Asserts that a value is false.

      expect(false).toBeFalse();
expect(true).not.toBeFalse();
expect(0).not.toBeFalse();
    • toBeFalsy(): void;

      Asserts that a value is "falsy".

      To assert that a value equals false, use toBe(false) instead.

      expect(true).toBeTruthy();
expect(1).toBeTruthy();
expect({}).toBeTruthy();
    • toBeFinite(): void;

      Asserts that a value is a number, and is not NaN or Infinity.

      expect(1).toBeFinite();
expect(3.14).toBeFinite();
expect(NaN).not.toBeFinite();
expect(Infinity).not.toBeFinite();
    • toBeFunction(): void;

      Asserts that a value is a function.

      expect(() => {}).toBeFunction();
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is greater than the expected value.

      @param expected

      the expected number

      expect(1).toBeGreaterThan(0);
expect(3.14).toBeGreaterThan(3);
expect(9).toBeGreaterThan(9); // fail
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is greater than or equal to the expected value.

      @param expected

      the expected number

      expect(1).toBeGreaterThanOrEqual(0);
expect(3.14).toBeGreaterThanOrEqual(3);
expect(9).toBeGreaterThanOrEqual(9);
    • value: unknown
      ): void;

      Asserts that the expected value is an instance of value

      expect([]).toBeInstanceOf(Array);
expect(null).toBeInstanceOf(Array); // fail
    • toBeInteger(): void;

      Asserts that a value is a number, and is an integer.

      expect(1).toBeInteger();
expect(3.14).not.toBeInteger();
expect(NaN).not.toBeInteger();
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is less than the expected value.

      @param expected

      the expected number

      expect(-1).toBeLessThan(0);
expect(3).toBeLessThan(3.14);
expect(9).toBeLessThan(9); // fail
    • expected: number | bigint
      ): void;

      Asserts that a value is a number and is less than or equal to the expected value.

      @param expected

      the expected number

      expect(-1).toBeLessThanOrEqual(0);
expect(3).toBeLessThanOrEqual(3.14);
expect(9).toBeLessThanOrEqual(9);
    • toBeNaN(): void;

      Asserts that a value is NaN.

      Same as using Number.isNaN().

      expect(NaN).toBeNaN();
expect(Infinity).toBeNaN(); // fail
expect("notanumber").toBeNaN(); // fail
    • toBeNegative(): void;

      Asserts that a value is a negative number.

      expect(-3.14).toBeNegative();
expect(1).not.toBeNegative();
expect(NaN).not.toBeNegative();
    • toBeNil(): void;

      Asserts that a value is null or undefined.

      expect(null).toBeNil();
expect(undefined).toBeNil();
    • toBeNull(): void;

      Asserts that a value is null.

      expect(null).toBeNull();
expect(undefined).toBeNull(); // fail
    • toBeNumber(): void;

      Asserts that a value is a number.

      expect(1).toBeNumber();
expect(3.14).toBeNumber();
expect(NaN).toBeNumber();
expect(BigInt(1)).not.toBeNumber();
    • toBeObject(): void;

      Asserts that a value is an object.

      expect({}).toBeObject();
expect("notAnObject").not.toBeObject();
expect(NaN).not.toBeObject();
    • toBeOdd(): void;

      Asserts that a number is odd.

      expect(1).toBeOdd();
expect(2).not.toBeOdd();
    • expected: unknown[] | Iterable<unknown, any, any>
      ): void;

      Asserts that the value is deep equal to an element in the expected array.

      The value must be an array or iterable, which includes strings.

      @param expected

      the expected value

      expect(1).toBeOneOf([1,2,3]);
expect("foo").toBeOneOf(["foo", "bar"]);
expect(true).toBeOneOf(new Set([true]));
    • toBePositive(): void;

      Asserts that a value is a positive number.

      expect(1).toBePositive();
expect(-3.14).not.toBePositive();
expect(NaN).not.toBePositive();
    • toBeString(): void;

      Asserts that a value is a string.

      expect("foo").toBeString();
expect(new String("bar")).toBeString();
expect(123).not.toBeString();
    • toBeSymbol(): void;

      Asserts that a value is a symbol.

      expect(Symbol("foo")).toBeSymbol();
expect("foo").not.toBeSymbol();
    • toBeTrue(): void;

      Asserts that a value is true.

      expect(true).toBeTrue();
expect(false).not.toBeTrue();
expect(1).not.toBeTrue();
    • toBeTruthy(): void;

      Asserts that a value is "truthy".

      To assert that a value equals true, use toBe(true) instead.

      expect(true).toBeTruthy();
expect(1).toBeTruthy();
expect({}).toBeTruthy();
    • type: 'string' | 'number' | 'bigint' | 'boolean' | 'symbol' | 'undefined' | 'object' | 'function'
      ): void;

      Asserts that a value matches a specific type.

      expect(1).toBeTypeOf("number");
expect("hello").toBeTypeOf("string");
expect([]).not.toBeTypeOf("boolean");
    • toBeUndefined(): void;

      Asserts that a value is undefined.

      expect(undefined).toBeUndefined();
expect(null).toBeUndefined(); // fail
    • toBeValidDate(): void;

      Asserts that a value is a valid Date object.

      expect(new Date()).toBeValidDate();
expect(new Date(null)).not.toBeValidDate();
expect("2020-03-01").not.toBeValidDate();
    • start: number,
      end: number
      ): void;

      Asserts that a value is a number between a start and end value.

      @param start

      the start number (inclusive)

      @param end

      the end number (exclusive)

    • expected: unknown
      ): void;

      Asserts that a value contains what is expected.

      The value must be an array or iterable, which includes strings.

      @param expected

      the expected value

      expect([1, 2, 3]).toContain(1);
expect(new Set([true])).toContain(true);
expect("hello").toContain("o");
    • expected: unknown
      ): void;

      Asserts that an object contains all the provided keys.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'hello', b: 'world' }).toContainAllKeys(['a','b']);
expect({ a: 'hello', b: 'world' }).toContainAllKeys(['b','a']);
expect({ 1: 'hello', b: 'world' }).toContainAllKeys([1,'b']);
expect({ a: 'hello', b: 'world' }).not.toContainAllKeys(['c']);
expect({ a: 'hello', b: 'world' }).not.toContainAllKeys(['a']);
    • expected: unknown
      ): void;

      Asserts that an object contain all the provided values.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainAllValues(['foo', 'bar', 'baz']);
expect(o).toContainAllValues(['baz', 'bar', 'foo']);
expect(o).not.toContainAllValues(['bar', 'foo']);
    • expected: unknown
      ): void;

      Asserts that an object contains at least one of the provided keys. Asserts that an object contains all the provided keys.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['a']);
expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['b']);
expect({ a: 'hello', b: 'world' }).toContainAnyKeys(['b', 'c']);
expect({ a: 'hello', b: 'world' }).not.toContainAnyKeys(['c']);
    • expected: unknown
      ): void;

      Asserts that an object contain any provided value.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainAnyValues(['qux', 'foo']);
expect(o).toContainAnyValues(['qux', 'bar']);
expect(o).toContainAnyValues(['qux', 'baz']);
expect(o).not.toContainAnyValues(['qux']);
    • expected: unknown
      ): void;

      Asserts that a value contains and equals what is expected.

      This matcher will perform a deep equality check for members of arrays, rather than checking for object identity.

      @param expected

      the expected value

      expect([{ a: 1 }]).toContainEqual({ a: 1 });
expect([{ a: 1 }]).not.toContainEqual({ a: 2 });
    • expected: unknown
      ): void;

      Asserts that an object contains a key.

      The value must be an object

      @param expected

      the expected value

      expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('a');
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('b');
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKey('c');
expect({ a: 'foo', b: 'bar', c: 'baz' }).not.toContainKey('d');
    • expected: unknown
      ): void;

      Asserts that an object contains all the provided keys.

      @param expected

      the expected value

      expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKeys(['a', 'b']);
expect({ a: 'foo', b: 'bar', c: 'baz' }).toContainKeys(['a', 'b', 'c']);
expect({ a: 'foo', b: 'bar', c: 'baz' }).not.toContainKeys(['a', 'b', 'e']);
    • expected: unknown
      ): void;

      Asserts that an object contain the provided value.

      The value must be an object

      @param expected

      the expected value

      const shallow = { hello: "world" };
const deep = { message: shallow };
const deepArray = { message: [shallow] };
const o = { a: "foo", b: [1, "hello", true], c: "baz" };

expect(shallow).toContainValue("world");
expect({ foo: false }).toContainValue(false);
expect(deep).toContainValue({ hello: "world" });
expect(deepArray).toContainValue([{ hello: "world" }]);

expect(o).toContainValue("foo", "barr");
expect(o).toContainValue([1, "hello", true]);
expect(o).not.toContainValue("qux");

// NOT
expect(shallow).not.toContainValue("foo");
expect(deep).not.toContainValue({ foo: "bar" });
expect(deepArray).not.toContainValue([{ foo: "bar" }]);
    • expected: unknown
      ): void;

      Asserts that an object contain the provided value.

      The value must be an object

      @param expected

      the expected value

      const o = { a: 'foo', b: 'bar', c: 'baz' };
expect(o).toContainValues(['foo']);
expect(o).toContainValues(['baz', 'bar']);
expect(o).not.toContainValues(['qux', 'foo']);
    • expected: string
      ): void;

      Asserts that a value ends with a string.

      @param expected

      the string to end with

    • expected: T
      ): void;

      Asserts that a value is deeply equal to what is expected.

      @param expected

      the expected value

      expect(100 + 23).toBe(123);
expect("d" + "og").toBe("dog");
expect([456]).toEqual([456]);
expect({ value: 1 }).toEqual({ value: 1 });
    • expected: string
      ): void;

      Asserts that a value is equal to the expected string, ignoring any whitespace.

      @param expected

      the expected string

      expect(" foo ").toEqualIgnoringWhitespace("foo");
expect("bar").toEqualIgnoringWhitespace(" bar ");

    • Ensures that a mock function is called.

    • expected: number
      ): void;

      Ensures that a mock function is called an exact number of times.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments.

    • ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the last call.

    • n: number,
      ...expected: unknown[]
      ): void;

      Ensure that a mock function is called with specific arguments for the nth call.

    • length: number
      ): void;

      Asserts that a value has a .length property that is equal to the expected length.

      @param length

      the expected length

      expect([]).toHaveLength(0);
expect("hello").toHaveLength(4);
    • keyPath: string | number | string | number[],
      value?: unknown
      ): void;

      Asserts that a value has a property with the expected name, and value if provided.

      @param keyPath

      the expected property name or path, or an index

      @param value

      the expected property value, if provided

      expect(new Set()).toHaveProperty("size");
expect(new Uint8Array()).toHaveProperty("byteLength", 0);
expect({ kitchen: { area: 20 }}).toHaveProperty("kitchen.area", 20);
expect({ kitchen: { area: 20 }}).toHaveProperty(["kitchen", "area"], 20);

    • Ensures that a mock function has returned successfully at least once.

      A promise that is unfulfilled will be considered a failure. If the function threw an error, it will be considered a failure.

    • times: number
      ): void;

      Ensures that a mock function has returned successfully at times times.

      A promise that is unfulfilled will be considered a failure. If the function threw an error, it will be considered a failure.

    • expected: string
      ): void;

      Asserts that a value includes a string.

      For non-string values, use toContain() instead.

      @param expected

      the expected substring

    • expected: string,
      times: number
      ): void;

      Asserts that a value includes a string {times} times.

      @param expected

      the expected substring

      @param times

      the number of times the substring should occur

    • expected: string | RegExp
      ): void;

      Asserts that a value matches a regular expression or includes a substring.

      @param expected

      the expected substring or pattern.

      expect("dog").toMatch(/dog/);
expect("dog").toMatch("og");
    • value?: string
      ): void;

      Asserts that a value matches the most recent inline snapshot.

      @param value

      The latest automatically-updated snapshot value.

      expect("Hello").toMatchInlineSnapshot();
expect("Hello").toMatchInlineSnapshot(`"Hello"`);
      propertyMatchers?: object,
      value?: string
      ): void;

      Asserts that a value matches the most recent inline snapshot.

      @param propertyMatchers

      Object containing properties to match against the value.

      @param value

      The latest automatically-updated snapshot value.

      expect({ c: new Date() }).toMatchInlineSnapshot({ c: expect.any(Date) });
expect({ c: new Date() }).toMatchInlineSnapshot({ c: expect.any(Date) }, `
{
  "v": Any<Date>,
}
`);
    • subset: object
      ): void;

      Asserts that an object matches a subset of properties.

      @param subset

      Subset of properties to match with.

      expect({ a: 1, b: 2 }).toMatchObject({ b: 2 });
expect({ c: new Date(), d: 2 }).toMatchObject({ d: 2 });
    • hint?: string
      ): void;

      Asserts that a value matches the most recent snapshot.

      @param hint

      Hint used to identify the snapshot in the snapshot file.

      expect([1, 2, 3]).toMatchSnapshot('hint message');
      propertyMatchers?: object,
      hint?: string
      ): void;

      Asserts that a value matches the most recent snapshot.

      @param propertyMatchers

      Object containing properties to match against the value.

      @param hint

      Hint used to identify the snapshot in the snapshot file.

      expect([1, 2, 3]).toMatchSnapshot();
expect({ a: 1, b: 2 }).toMatchSnapshot({ a: 1 });
expect({ c: new Date() }).toMatchSnapshot({ c: expect.any(Date) });
    • predicate: (value: T) => boolean
      ): void;

      Checks whether a value satisfies a custom condition.

      @param predicate

      The custom condition to be satisfied. It should be a function that takes a value as an argument (in this case the value from expect) and returns a boolean.

      expect(1).toSatisfy((val) => val > 0);
expect("foo").toSatisfy((val) => val === "foo");
expect("bar").not.toSatisfy((val) => val === "bun");
    • expected: string
      ): void;

      Asserts that a value starts with a string.

      @param expected

      the string to start with

    • expected: T
      ): void;

      Asserts that a value is deeply and strictly equal to what is expected.

      There are two key differences from toEqual():

      1. It checks that the class is the same.
      2. It checks that undefined values match as well.
      @param expected

      the expected value

      class Dog {
  type = "dog";
}
const actual = new Dog();
expect(actual).toStrictEqual(new Dog());
expect(actual).toStrictEqual({ type: "dog" }); // fail
    • expected?: unknown
      ): void;

      Asserts that a function throws an error.

      • If expected is a string or RegExp, it will check the message property.
      • If expected is an Error object, it will check the name and message properties.
      • If expected is an Error constructor, it will check the class of the Error.
      • If expected is not provided, it will check if anything has thrown.
      @param expected

      the expected error, error message, or error pattern

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrow("Oops!");
expect(fail).toThrow(/oops/i);
expect(fail).toThrow(Error);
expect(fail).toThrow();
    • expected?: unknown
      ): void;

      Asserts that a function throws an error.

      • If expected is a string or RegExp, it will check the message property.
      • If expected is an Error object, it will check the name and message properties.
      • If expected is an Error constructor, it will check the class of the Error.
      • If expected is not provided, it will check if anything has thrown.
      @param expected

      the expected error, error message, or error pattern

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowError("Oops!");
expect(fail).toThrowError(/oops/i);
expect(fail).toThrowError(Error);
expect(fail).toThrowError();
    • value?: string
      ): void;

      Asserts that a function throws an error matching the most recent snapshot.

      @param value

      The latest automatically-updated snapshot value.

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowErrorMatchingInlineSnapshot();
expect(fail).toThrowErrorMatchingInlineSnapshot(`"Oops!"`);
    • hint?: string
      ): void;

      Asserts that a function throws an error matching the most recent snapshot.

      function fail() {
  throw new Error("Oops!");
}
expect(fail).toThrowErrorMatchingSnapshot();
expect(fail).toThrowErrorMatchingSnapshot("This one should say Oops!");

  • interface Test

    Runs a test.

    test("can check if using Bun", () => {
  expect(Bun).toBeDefined();
});

test("can make a fetch() request", async () => {
  const response = await fetch("https://example.com/");
  expect(response.ok).toBe(true);
});

test("can set a timeout", async () => {
  await Bun.sleep(100);
}, 50); // or { timeout: 50 }
    • each<T extends readonly [any, any]>(
      table: readonly T[]
      ): (label: string, fn: (...args: [...T[]]) => void | Promise<unknown>, options?: number | TestOptions) => void;

      Returns a function that runs for each item in table.

      @param table

      Array of Arrays with the arguments that are passed into the test fn for each row.

      each<T extends any[]>(
      table: readonly T[]
      ): (label: string, fn: (...args: Readonly<T>) => void | Promise<unknown>, options?: number | TestOptions) => void;
      each<T>(
      table: T[]
      ): (label: string, fn: (...args: T[]) => void | Promise<unknown>, options?: number | TestOptions) => void;
    • label: string,
      fn?: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void,
      options?: number | TestOptions
      ): void;

      Marks this test as failing.

      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.

      test.failing is very similar to test.todo except that it always runs, regardless of the --todo flag.

      @param label

      the label for the test

      @param fn

      the test function

      @param options

      the test timeout or options

    • condition: boolean
      ): (label: string, fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void, options?: number | TestOptions) => void;

      Runs this test, if condition is true.

      This is the opposite of test.skipIf().

      @param condition

      if the test should run

    • label: string,
      fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void,
      options?: number | TestOptions
      ): void;

      Skips all other tests, except this test when run with the --only option.

      @param label

      the label for the test

      @param fn

      the test function

      @param options

      the test timeout or options

    • label: string,
      fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void,
      options?: number | TestOptions
      ): void;

      Skips this test.

      @param label

      the label for the test

      @param fn

      the test function

      @param options

      the test timeout or options

    • condition: boolean
      ): (label: string, fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void, options?: number | TestOptions) => void;

      Skips this test, if condition is true.

      @param condition

      if the test should be skipped

    • label: string,
      fn?: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void,
      options?: number | TestOptions
      ): void;

      Marks this test as to be written or to be fixed.

      These tests will not be executed unless the --todo flag is passed. With the flag, if the test passes, the test will be marked as fail in the results; you will have to remove the .todo or check that your test is implemented correctly.

      @param label

      the label for the test

      @param fn

      the test function

      @param options

      the test timeout or options

    • condition: boolean
      ): (label: string, fn: () => void | Promise<unknown> | (done: (err?: unknown) => void) => void, options?: number | TestOptions) => void;

      Marks this test as to be written or to be fixed, if condition is true.

      @param condition

      if the test should be marked TODO

  • interface TestOptions

    • repeats?: number

      Sets the number of times to repeat the test, regardless of whether it passed or failed.

    • retry?: number

      Sets the number of times to retry the test if it fails.

    • timeout?: number

      Sets the timeout for the test in milliseconds.

      If the test does not complete within this time, the test will fail with:

      'Timeout: test {name} timed out after 5000ms'
  • type AsymmetricMatcher = any

    Object representing an asymmetric matcher obtained by an static call to expect like expect.anything(), expect.stringContaining("..."), etc.

  • type CustomMatcher<E, P extends any[]> = (this: MatcherContext, expected: E, ...matcherArguments: P) => MatcherResult | Promise<MatcherResult>
  • type CustomMatchersDetected = Omit<Matchers<unknown>, keyof MatchersBuiltin<unknown>> & Omit<AsymmetricMatchers, keyof AsymmetricMatchersBuiltin>

    All non-builtin matchers and asymmetric matchers that have been type-registered through declaration merging

  • type EqualsFunction = (a: unknown, b: unknown) => boolean
  • type ExpectExtendMatchers<M> = { [K in keyof M]: k extends keyof CustomMatchersDetected ? CustomMatcher<unknown, Parameters<CustomMatchersDetected[k]>> : CustomMatcher<unknown, any[]> }

    If the types has been defined through declaration merging, enforce it. Otherwise enforce the generic custom matcher signature.

  • type Mock<T extends (...args: any[]) => any> = JestMock.Mock<T>

    -- Mocks --

  • type Tester = (this: TesterContext, a: any, b: any, customTesters: Tester[]) => boolean | undefined

    Custom equality tester