Matchers

Latte provides a set of built-in matchers that can be used to assert conditions in your tests. These matchers are designed to be easy to use and understand, making it simple to write clear and concise test cases.

To use a matcher, you need to call expect, which will return an instance of Expect, which, in turn, will make it possible to call the corresponding matcher on the specified value.

You can use the matcher in two ways:

expect(value).toBe(expectedValue)

expect(value).not.toBe(expectedValue)

Positive Tests

By default, the matcher checks if the value is equal to the expected value (positive test). If it is, the test will pass; otherwise, it will fail.

If in expect you pass the value to be tested, then in matcher you specify a control value that must either match the value being tested or not. Also, in the matcher, you can pass your custom error message.

test(`Common tests suite`, () => {
    expect(1 + 1).toBe(2, `1 + 1 should be 2`)
})

Negative Tests

If you want to check that the value is not equal to the expected value, you can use the not modifier:

expect(value).not.toBe(expectedValue)

Chaining Matchers

You can chain multiple matchers together to create more complex assertions. For example:

expect(value)
    .toBeDefined()
    .toBeType('string')
    .toBe(expectedValue)

Base

toBe()

toBe(expected, msg?: string)

Asserts that the actual value is equal to the expected value. Matcher uses the Object.is() method to compare values.

toBeStrictEqual()

toBeStrictEqual(expected, msg?: string)

Asserts that the actual value is strict equal (uses ===) to the expected value.

toBeEqual()

toBeEqual(expected, msg?: string)

Asserts that the actual value is equal (uses ==) to the expected value.

Array

toBeArrayEqual()

toBeArrayEqual(expected, msg?: string)

Asserts that the actual array is equal to the expected array.

toBeArray()

toBeArray(msg?: string)

Asserts that the actual value is an array.

toBeArraySorted()

toBeArraySorted(msg?: string)

Asserts that the actual value is sorted.

toBeArrayUnique()

toBeArrayUnique(msg?: string)

Asserts that values in the array are unique.

toContain()

toContain(expected, msg?: string)

Asserts that the actual value contains the expected value.

toBeEmpty()

toBeEmpty(msg?: string)

Asserts that the actual value is empty.

hasLength()

hasLength(expected, msg?: string)

Asserts that the array-like object has the expected length.

toBeArrayBuffer()

toBeArrayBuffer(msg?: string)

Asserts that the actual value is an ArrayBuffer.

Async

toBeResolvedWith()

toBeResolvedWith(expected, msg?: string)

Asserts that the actual promise resolves with the expected value.

toBeRejectedWith()

toBeRejectedWith(expected, msg?: string) Asserts that the actual promise rejects with the expected value.

Color

toBeHEXColor()

toBeHEXColor(msg?: string)

Asserts that the actual value is a HEX color.

toBeRGBColor()

toBeRGBColor(msg?: string)

Asserts that the actual value is an RGB color.

toBeRGBAColor()

toBeRGBAColor(msg?: string)

Asserts that the actual value is an RGBA color.

toBeHSVColor()

toBeHSVColor(msg?: string)

Asserts that the actual value is an HSL color.

toBeHSLColor()

toBeHSLColor(msg?: string)

Asserts that the actual value is an HSL color.

toBeHSLAColor()

toBeHSLAColor(msg?: string)

Asserts that the actual value is an HSLA color.

toBeCMYKColor()

toBeCMYKColor(msg?: string)

Asserts that the actual value is a CMYK color.

toBeColor()

toBeColor(msg?: string)

Asserts that the actual value is a valid color (HEX, RGB, RGBA, HSV, HSL, HSLA, or CMYK).

Html

toBeHtmlElement()

toBeHtmlElement(msg?: string)

Asserts that the actual value is an HTML element.

toBeNode()

toBeNode(msg?: string)

Asserts that the actual value is an HTML node.

toBeDocument()

toBeDocument(msg?: string)

Asserts that the actual value is an HTML document.

toBeHtmlCollection()

toBeHtmlCollection(msg?: string)

Asserts that the actual value is an HTML collection.

toBeWindow()

toBeWindow(msg?: string)

Asserts that the actual value is a Window object.

toBeTextNode()

toBeTextNode(msg?: string)

Asserts that the actual value is a Text node.

hasClass()

hasClass(expected, msg?: string)

Asserts that the HTML element has the specified class.

hasAttribute()

hasAttribute(expected, msg?: string)

Asserts that the HTML element has the specified attribute.

hasChildren()

hasChildren(msg?: string)

Asserts that the HTML element has children.

hasParent()

hasParent(msg?: string)

Asserts that the HTML element has a parent.

hasStyleProperty()

hasStyleProperty(expected, msg?: string)

Asserts that the HTML element has the specified style in style property.

hasStyle()

hasStyle(prop, val, msg?: string)

Asserts that the HTML element has the specified style property.

hasStyles()

hasStyles(styles: object, msg?: string)

Asserts that the HTML element has the specified styles.

hasSiblings()

hasSiblings(msg?: string)

Asserts that the HTML element has siblings.

hasSibling()

hasSibling(expected: HTMLElement, msg?: string)

Asserts that the HTML element has a sibling with the specified value.

hasPrev()

hasPrev(msg?: string)

Asserts that the HTML element has a previous sibling.

hasNext()

hasNext(msg?: string)

Asserts that the HTML element has a next sibling.

hasText()

hasText(expected, msg?: string)

Asserts that the HTML element has the specified text.

containsElement()

containsElement(expected, msg?: string)

Asserts that the HTML element contains the specified element.

containsElementDeep()

containsElementDeep(expected, msg?: string)

Asserts that the HTML element contains the specified element deeply.

hasId()

hasId(expected, msg?: string) Asserts that the HTML element has the specified id.

hasName()

hasName(expected, msg?: string) Asserts that the HTML element has the specified name.

hasHref()

hasHref(expected, msg?: string) Asserts that the HTML element has the specified href.

hasSrc()

hasSrc(expected, msg?: string) Asserts that the HTML element has the specified src.

Mock

toHaveBeenCalled()

toHaveBeenCalled(msg?: string)

Asserts the mock function was called at least once

toHaveBeenCalledTimes()

toHaveBeenCalledTimes(expected, msg?: string)

Asserts the mock function was called at least once

toHaveBeenCalledWith()

toHaveBeenCalledWith(expected, msg?: string)

Asserts that the mock function was called with specified arguments.

toHaveBeenLastCalledWith()

toHaveBeenLastCalledWith(expected, msg?: string)

Asserts that the mock function was called last with specified arguments.

Object

toBeObject()

toBeObject(expected, msg?: string)

Asserts that the actual object is equal to the expected object. Checks only own level properties and values.

toBeDeepEqual()

toBeDeepEqual(expected, msg?: string)

Asserts that the actual value is deeply equal to the expected value.

toBeDeepEqualSafe()

toBeDeepEqualSafe(expected, msg?: string)

Asserts that the actual value is deeply equal to the expected value using a safe comparison.

toBeObjectStructureEqual()

toBeObjectStructureEqual(expected, msg?: string)

Asserts that the actual structure is equal to the expected structure.

hasProperty()

hasProperty(expected, msg?: string)

Asserts that the actual value has the specified property. You can use dot notation to check for nested properties.

hasPropertyValue()

hasPropertyValue(expected, value, msg?: string) Asserts that the actual value has the specified property with the expected value. You can use dot notation to check for nested properties.

Throw

toThrow()

toThrow(msg?: string)

Asserts that the actual function throws an error.

toThrowError()

toThrowError(expected, msg?: string)

Asserts that the actual function throws an error matching the expected value.

Type

toBeType()

toBeType(type, msg?: string)

Asserts that the actual value is of the specified type.

toBeInstanceOf()

toBeInstanceOf(type, msg?: string)

Asserts that the actual value is an instance of the specified type.

toBeString()

toBeString(msg?: string)

Asserts that the actual value is a string.

toBeFunction()

toBeFunction(msg?: string)

Asserts that the actual value is a function.

toBeAsyncFunction()

toBeAsyncFunction(msg?: string)

Asserts that the actual value is an async function.

toBeDate()

toBeDate(msg?: string)

Asserts that the actual value is a date.

toBeDateObject()

toBeDateObject(msg?: string)

Asserts that the actual value is a date.

toBeRegExp()

toBeRegExp(msg?: string)

Asserts that the actual value is a regular expression.

toBeSymbol()

toBeSymbol(msg?: string)

Asserts that the actual value is a symbol.

toBeBigInt()

toBeBigInt(msg?: string)

Asserts that the actual value is a BigInt.

toBeMap()

toBeMap(msg?: string)

Asserts that the actual value is a Map.

toBeSet()

toBeSet(msg?: string)

Asserts that the actual value is a Set.

toBeWeakMap()

toBeWeakMap(msg?: string)

Asserts that the actual value is a WeakMap.

toBeWeakSet()

toBeWeakSet(msg?: string)

Asserts that the actual value is a WeakSet.

toBeNumber()

toBeNumber(msg?: string)

Asserts that the actual value is a number and not is NaN.

toBeNaN()

toBeNaN(msg?: string)

Asserts that the actual value is NaN.

toBeInteger()

toBeInteger(msg?: string)

Asserts that the actual value is an integer.

toBeSafeInteger()

toBeSafeInteger(msg?: string)

Asserts that the actual value is a safe integer.

toBeFloat()

toBeFloat(msg?: string)

Asserts that the actual value is a float.

toBeBoolean()

toBeBoolean(msg?: string)

Asserts that the actual value is a boolean.

toBeDefined()

toBeDefined(msg?: string)

Asserts that the actual value is defined.

toBeUndefined()

toBeUndefined(msg?: string)

Asserts that the actual value is undefined.

toBeNull()

toBeNull(msg?: string)

Asserts that the actual value is null.

toBePromise()

toBePromise(msg?: string)

Asserts that the actual value is a Promise.

toBeJson()

toBeJson(msg?: string)

Asserts that the actual value is a JSON string.

toBeXml()

toBeXml(msg?: string)

Asserts that the actual value is an XML string.

Validator

toBeBase64()

toBeBase64(msg?: string)

Asserts that the actual value is a Base64 encoded string.

toBeIP()

toBeIP(msg?: string)

Asserts that the actual value is a valid IP address.

toBeIPv4()

toBeIPv4(msg?: string)

Asserts that the actual value is a valid IPv4 address.

toBeIPv6()

toBeIPv6(msg?: string)

Asserts that the actual value is a valid IPv6 address.

toBeEmail()

toBeEmail(msg?: string)

Asserts that the actual value is a valid email address.

toBeUrl()

toBeUrl(msg?: string)

Asserts that the actual value is a valid URL.

toBeCloseTo()

toBeCloseTo(expected, precision = 2, msg?: string)

Asserts that the actual value is close to the expected value within a certain precision.

toBePositive()

toBePositive(msg?: string)

Asserts that the actual value is positive.

toBeNegative()

toBeNegative(msg?: string)

Asserts that the actual value is negative.

toBeFinite()

toBeFinite(msg?: string)

Asserts that the actual value is finite.

toBeGreaterThan()

toBeGreaterThan(expected, msg?: string)

Asserts that the actual value is greater than the expected value.

toBeGreaterThanOrEqual()

toBeGreaterThanOrEqual(expected, msg?: string)

Asserts that the actual value is greater than or equal to the expected value.

toBeLessThan()

toBeLessThan(expected, msg?: string)

Asserts that the actual value is less than the expected value.

toBeLessThanOrEqual()

toBeLessThanOrEqual(expected, msg?: string)

Asserts that the actual value is less than or equal to the expected value.

toBetween()

toBetween(min, max, msg?: string)

Asserts that the actual value is between the specified minimum and maximum values.

toBeMatch()

toMatch(expected, msg?: string)

Asserts that the actual value matches the expected RegExp pattern.

toBeTrue()

toBeTrue(msg?: string)

Asserts that the actual value is true.

toBeFalse()

toBeFalse(msg?: string)

Asserts that the actual value is false.

hasAriaAttribute()

hasAriaAttribute(expected, msg?: string) Asserts that the HTML element has the specified ARIA attribute.

hasAriaAttributes()

hasAriaAttributes(expected, msg?: string) Asserts that the HTML element has the specified ARIA attributes. expected is a space-separated string of attributes.

hasAriaRole()

hasAriaRole(expected, msg?: string) Asserts that the HTML element has the specified ARIA role.

hasAriaLabel()

hasAriaLabel(expected, msg?: string) Asserts that the HTML element has the specified ARIA label.

hasAltText()

hasAltText(msg?: string) Asserts that the HTML element has the specified alt text.

toBeKeyboardAccessible()

toBeKeyboardAccessible(msg?: string)

React

toRenderWithoutError()

toRenderWithoutError(msg?: string)

Asserts that the React component renders without throwing an error.

toRenderText()

toRenderText(expected, msg?: string) Asserts that the React component renders with the specified text.

toContainElement()

toContainElement(expected, msg?: string) Asserts that the React component contains the specified element.

toHaveElementCount()

toHaveElementCount(expected, msg?: string) Asserts that the React component has the specified number of elements.

toTriggerEvent()

toTriggerEvent(selector, event, callback, data, msg?: string) Asserts that the React component triggers the specified event.

toEventuallyContain

toEventuallyContain(selector, timeout, msg?: string)

Asserts that the React component eventually contains the specified element within the given timeout.