deep-assert

deep-assert

Providing a better deep-equals assertion experience.

• Easily write object and array expectations, with any() and satisfies()
• Create your own custom assertions
• Short, but precise diffs, even for large nested objects
• Works with objects, arrays, dates, buffers, etc
• Zero dependencies

Installation

npm install deep-assert

Usage

Basic

Let's say we want to check if an array of user objects matches our expectation, but we don't know what the id is gonna be, since it's a random ID. It's easy, using any().

import * as assert from "assert-deep"

assert.deepEquals(getUsers(), [
  {
    id: assert.any(),
    name: "John Smith",
    active: true
  },
  {
    id: assert.any(),
    name: "Jane Smith",
    active: false
  }
])

Custom assertions

Let's try the previous use case again, but this time we check that the id is a valid UUIDv4. We use the satisfies() helper function to create a custom assertion to be used within the object expectation.

import * as assert from "assert-deep"

const uuidRegex = /^[0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{12}$/
const assertUUID = assert.satisfies(value => typeof value === "string" && value.match(uuidRegex))

assert.deepEquals(getUsers(), [
  {
    id: assertUUID(),
    name: "John Smith",
    active: true
  },
  {
    id: assertUUID(),
    name: "Jane Smith",
    active: false
  }
])

Spreading any()

Normally deepEquals() will fail if there are unexpected properties on the tested object. We can use any() with the object spread operator to allow additional properties to be present.

deepEquals() will then only check the expected properties and ignore all other ones.

import * as assert from "assert-deep"

assert.deepEquals(getUsers()[0], {
  name: "John Smith",
  active: true,
  ...assert.any()
})

Recursive objects

import * as assert from "assert-deep"

const a = { foo: {} }
a.foo.parent = a.foo

assert.deepEquals(a, {
  foo: assert.satisfies(foo => assert.deepEquals(foo, { parent: foo }))
})

License

MIT