Jest Matchers Cheat sheet

A quick reference for commonly used jest matchers. A full list can be found on their docs page

toBe

• For exact match (Not for different objects or arrays)
• Uses Object.is for equality check

toEqual

• For exact match of arrays and objects
• Recursively checks every field of an object or array.
• Ignores undefined or empty values

toStrictEqual

• For additionally checking the equality of data types as well
• For example, checking the difference between instance of User class and an user object literal having same props as the instance.
• .toEqual will pass it as same objects but nto .toStrictEqual

NOTE: A great article explaining detailed difference between toEqual and toStrictEqual

not

• Opposite of matcher
• To test something like .not.toBe()

Truthiness

• toBeNull matches only null
• toBeUndefined matches only undefined
• toBeDefined is the opposite of toBeUndefined
• toBeTruthy matches anything that an if statement treats as true
• toBeFalsy matches anything that an if statement treats as false

Numbers

• toBeGreaterThan
• toBeGreaterThanOrEqual
• toBeLessThan
• toBeLessThanOrEqual
• toBe and toEqual are equivalent for numbers
• toBeCloseTo for floating points. Can be used to avoid small rounding errors while testing.

Strings

• toMatch for checking strings against regular expressions.

Arrays and iterables

• toContain to check if an item exist in an array or iterable (Example a Set)

Exceptions

• toThrow to test thrown errors by functions
• It accepts an Error, string or regular expression to compare the thrown Error or message.

TIP: For more Jest matchers, check out jest-extended