bun:test MatchersBuiltin TypeScript interface | API Reference | Bun

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BuildDocsReferenceGuidesBlogDiscord/bun:test/MatchersBuiltinPfailMlastCalledWithPnotMnthCalledWithPpassPrejectsPresolvesMtoBeMtoBeArrayMtoBeArrayOfSizeMtoBeBooleanMtoBeCalledMtoBeCalledTimesMtoBeCalledWithMtoBeCloseToMtoBeDateMtoBeDefinedMtoBeEmptyMtoBeEmptyObjectMtoBeEvenMtoBeFalseMtoBeFalsyMtoBeFiniteMtoBeFunctionMtoBeGreaterThanMtoBeGreaterThanOrEqualMtoBeInstanceOfMtoBeIntegerMtoBeLessThanMtoBeLessThanOrEqualMtoBeNaNMtoBeNegativeMtoBeNilMtoBeNullMtoBeNumberMtoBeObjectMtoBeOddMtoBeOneOfMtoBePositiveMtoBeStringMtoBeSymbolMtoBeTrueMtoBeTruthyMtoBeTypeOfMtoBeUndefinedMtoBeValidDateMtoBeWithinMtoContainMtoContainAllKeysMtoContainAllValuesMtoContainAnyKeysMtoContainAnyValuesMtoContainEqualMtoContainKeyMtoContainKeysMtoContainValueMtoContainValuesMtoEndWithMtoEqualMtoEqualIgnoringWhitespaceMtoHaveBeenCalledMtoHaveBeenCalledTimesMtoHaveBeenCalledWithMtoHaveBeenLastCalledWithMtoHaveBeenNthCalledWithMtoHaveLastReturnedWithMtoHaveLengthMtoHaveNthReturnedWithMtoHavePropertyMtoHaveReturnedMtoHaveReturnedTimesMtoHaveReturnedWithMtoIncludeMtoIncludeRepeatedMtoMatchMtoMatchInlineSnapshotMtoMatchObjectMtoMatchSnapshotMtoSatisfyMtoStartWithMtoStrictEqualMtoThrowMtoThrowErrorMtoThrowErrorMatchingInlineSnapshotMtoThrowErrorMatchingSnapshot

interface

test.MatchersBuiltininterface MatchersBuiltinT = unknown>fail: (message?: string) => voidAssertion which fails.

expect().fail(); expect().fail("message is optional"); expect().not.fail(); expect().not.fail("hi"); not: Matchersunknown>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) => voidAssertion which passes.

expect().pass(); expect().pass("message is optional"); expect().not.pass(); expect().not.pass("hi"); rejects: Matchersunknown>Expects the value to be a promise that rejects.

expect(Promise.reject("error")).rejects.toBe("error"); resolves: MatchersAwaitedT>>Expects the value to be a promise that resolves.

expect(Promise.resolve(1)).resolves.toBe(1); lastCalledWith(...expected: unknown[]): void;Ensure that a mock function is called with specific arguments for the nth call.

nthCalledWith(n: number,...expected: unknown[]): void;Ensure that a mock function is called with specific arguments for the nth call.

toBe(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 expectedthe 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() // TypeScript errors: expect("hello").toBe(3.14); // typescript error + fail expect("hello").toBenumber>(3.14); // no typescript error, but still fails toBeX = T>(expected: NoInferX>): void;toBeArray(): void;Asserts that a value is a array.

expect([1]).toBeArray(); expect(new Array(1)).toBeArray(); expect({}).not.toBeArray(); toBeArrayOfSize(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.

toBeCalledTimes(expected: number): void;Ensure that a mock function is called with specific arguments.

toBeCalledWith(...expected: unknown[]): void;Ensure that a mock function is called with specific arguments.

toBeCloseTo(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 expectedthe expected value

@param numDigitsthe 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(); toBeEmptyObject(): void;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(); toBeGreaterThan(expected: number | bigint): void;Asserts that a value is a number and is greater than the expected value.

@param expectedthe expected number

expect(1).toBeGreaterThan(0); expect(3.14).toBeGreaterThan(3); expect(9).toBeGreaterThan(9); // fail toBeGreaterThanOrEqual(expected: number | bigint): void;Asserts that a value is a number and is greater than or equal to the expected value.

@param expectedthe expected number

expect(1).toBeGreaterThanOrEqual(0); expect(3.14).toBeGreaterThanOrEqual(3); expect(9).toBeGreaterThanOrEqual(9); toBeInstanceOf(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(); toBeLessThan(expected: number | bigint): void;Asserts that a value is a number and is less than the expected value.

@param expectedthe expected number

expect(-1).toBeLessThan(0); expect(3).toBeLessThan(3.14); expect(9).toBeLessThan(9); // fail toBeLessThanOrEqual(expected: number | bigint): void;Asserts that a value is a number and is less than or equal to the expected value.

@param expectedthe 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(); toBeOneOf(expected: IterableT>): 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 expectedthe expected value

expect(1).toBeOneOf([1,2,3]); expect("foo").toBeOneOf(["foo", "bar"]); expect(true).toBeOneOf(new Set([true])); toBeOneOfX = T>(expected: NoInferIterableX, any, any>>): void;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(); toBeTypeOf(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(); toBeWithin(start: number,end: number): void;Asserts that a value is a number between a start and end value.

@param startthe start number (inclusive)

@param endthe end number (exclusive)

toContain(expected: T extends IterableU, any, any> ? U : T): void;Asserts that a value contains what is expected.

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

@param expectedthe expected value

expect([1, 2, 3]).toContain(1); expect(new Set([true])).toContain(true); expect("hello").toContain("o"); toContainX = T>(expected: NoInferX extends IterableU, any, any> ? U : X>): void;toContainAllKeys(expected: IfNeverThenElsekeyof T, PropertyKey>[]): void;Asserts that an object contains all the provided keys.

The value must be an object

@param expectedthe 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']); toContainAllKeysX = T>(expected: IfNeverThenElseNoInferkeyof X>, PropertyKey>[]): void;toContainAllValues(expected: unknown[]): void;Asserts that an object contain all the provided values.

The value must be an object

@param expectedthe 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']); toContainAnyKeys(expected: IfNeverThenElsekeyof T, PropertyKey>[]): 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 expectedthe 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']); toContainAnyKeysX = T>(expected: IfNeverThenElseNoInferkeyof X>, PropertyKey>[]): void;toContainAnyValues(expected: unknown[]): void;Asserts that an object contain any provided value.

The value must be an object

@param expectedthe 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']); toContainEqual(expected: T extends IterableU, any, any> ? U : T): 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 expectedthe expected value

expect([{ a: 1 }]).toContainEqual({ a: 1 }); expect([{ a: 1 }]).not.toContainEqual({ a: 2 }); toContainEqualX = T>(expected: NoInferX extends IterableU, any, any> ? U : X>): void;toContainKey(expected: IfNeverThenElsekeyof T, PropertyKey>): void;Asserts that an object contains a key.

The value must be an object

@param expectedthe 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'); toContainKeyX = T>(expected: IfNeverThenElseNoInferkeyof X>, PropertyKey>): void;toContainKeys(expected: IfNeverThenElsekeyof T, PropertyKey>[]): void;Asserts that an object contains all the provided keys.

@param expectedthe 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']); toContainKeysX = T>(expected: IfNeverThenElseNoInferkeyof X>, PropertyKey>[]): void;toContainValue(expected: unknown): void;Asserts that an object contain the provided value.

This method is deep and will look through child properties to find the expected value.

The input value must be an object.

@param expectedthe 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" }]); toContainValues(expected: unknown[]): void;Asserts that an object contain the provided value.

This is the same as toContainValue, but accepts an array of values instead.

The value must be an object

@param expectedthe 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']); toEndWith(expected: string): void;Asserts that a value ends with a string.

@param expectedthe string to end with

toEqual(expected: T): void;Asserts that a value is deeply equal to what is expected.

@param expectedthe expected value

expect(100 + 23).toBe(123); expect("d" + "og").toBe("dog"); expect([456]).toEqual([456]); expect({ value: 1 }).toEqual({ value: 1 }); toEqualX = T>(expected: NoInferX>): void;toEqualIgnoringWhitespace(expected: string): void;Asserts that a value is equal to the expected string, ignoring any whitespace.

@param expectedthe expected string

expect(" foo ").toEqualIgnoringWhitespace("foo"); expect("bar").toEqualIgnoringWhitespace(" bar "); toHaveBeenCalled(): void;Ensures that a mock function is called.

toHaveBeenCalledTimes(expected: number): void;Ensures that a mock function is called an exact number of times.

toHaveBeenCalledWith(...expected: unknown[]): void;Ensure that a mock function is called with specific arguments.

toHaveBeenLastCalledWith(...expected: unknown[]): void;Ensure that a mock function is called with specific arguments for the last call.

toHaveBeenNthCalledWith(n: number,...expected: unknown[]): void;Ensure that a mock function is called with specific arguments for the nth call.

toHaveLastReturnedWith(expected: unknown): void;Ensures that a mock function has returned a specific value on its last invocation. This matcher uses deep equality, like toEqual(), and supports asymmetric matchers.

toHaveLength(length: number): void;Asserts that a value has a .length property that is equal to the expected length.

@param lengththe expected length

expect([]).toHaveLength(0); expect("hello").toHaveLength(4); toHaveNthReturnedWith(n: number,expected: unknown): void;Ensures that a mock function has returned a specific value on the nth invocation. This matcher uses deep equality, like toEqual(), and supports asymmetric matchers.

@param nThe 1-based index of the function call

@param expectedThe expected return value

toHaveProperty(keyPath: string | number | string | number[],value?: unknown): void;Asserts that a value has a property with the expected name, and value if provided.

@param keyPaththe expected property name or path, or an index

@param valuethe 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); toHaveReturned(): void;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.

toHaveReturnedTimes(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.

toHaveReturnedWith(expected: unknown): void;Ensures that a mock function has returned a specific value. This matcher uses deep equality, like toEqual(), and supports asymmetric matchers.

toInclude(expected: string): void;Asserts that a value includes a string.

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

@param expectedthe expected substring

toIncludeRepeated(expected: string,times: number): void;Asserts that a value includes a string {times} times.

@param expectedthe expected substring

@param timesthe number of times the substring should occur

toMatch(expected: string | RegExp): void;Asserts that a value matches a regular expression or includes a substring.

@param expectedthe expected substring or pattern.

expect("dog").toMatch(/dog/); expect("dog").toMatch("og"); toMatchInlineSnapshot(value?: string): void;Asserts that a value matches the most recent inline snapshot.

@param valueThe latest automatically-updated snapshot value.

expect("Hello").toMatchInlineSnapshot(); expect("Hello").toMatchInlineSnapshot(`"Hello"`); toMatchInlineSnapshot(propertyMatchers?: object,value?: string): void;Asserts that a value matches the most recent inline snapshot.

@param propertyMatchersObject containing properties to match against the value.

@param valueThe 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, } `); toMatchObject(subset: object): void;Asserts that an object matches a subset of properties.

@param subsetSubset of properties to match with.

expect({ a: 1, b: 2 }).toMatchObject({ b: 2 }); expect({ c: new Date(), d: 2 }).toMatchObject({ d: 2 }); toMatchSnapshot(hint?: string): void;Asserts that a value matches the most recent snapshot.

@param hintHint used to identify the snapshot in the snapshot file.

expect([1, 2, 3]).toMatchSnapshot('hint message'); toMatchSnapshot(propertyMatchers?: object,hint?: string): void;Asserts that a value matches the most recent snapshot.

@param propertyMatchersObject containing properties to match against the value.

@param hintHint 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) }); toSatisfy(predicate: (value: T) => boolean): void;Checks whether a value satisfies a custom condition.

@param predicateThe 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"); toStartWith(expected: string): void;Asserts that a value starts with a string.

@param expectedthe string to start with

toStrictEqual(expected: T): void;Asserts that a value is deeply and strictly equal to what is expected.

There are two key differences from toEqual():

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

class Dog { type = "dog"; } const actual = new Dog(); expect(actual).toStrictEqual(new Dog()); expect(actual).toStrictEqual({ type: "dog" }); // fail toStrictEqualX = T>(expected: NoInferX>): void;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 expectedthe 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(); toThrowError(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 expectedthe 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(); toThrowErrorMatchingInlineSnapshot(value?: string): void;Asserts that a function throws an error matching the most recent snapshot.

@param valueThe latest automatically-updated snapshot value.

function fail() { throw new Error("Oops!"); } expect(fail).toThrowErrorMatchingInlineSnapshot(); expect(fail).toThrowErrorMatchingInlineSnapshot(`"Oops!"`); toThrowErrorMatchingSnapshot(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!");

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