Assert module in nodeJS

Introduction

The assert module provides a set of assertion functions for verifying invariants
We will learn the most used assertion functions

Common assertion functions

assert.deepEqual()
assert.equal()
assert.notDeepEqual()
assert.notEqual()

assert.deepEqual()

Tests for deep equality between the actual and expected parameters

Comparison details

Primitive values are compared with the Abstract Equality Comparison ( == ) with the exception of NaN.
It is treated as being identical in case both sides are NaN.
Type tags of objects should be the same.
Only enumerable own properties are considered.
Error names and messages are always compared, even if these are not enumerable properties
Object wrappers are compared both as objects and unwrapped values.
Object properties are compared unordered.
Map keys and Set items are compared unordered.
Recursion stops when both sides differ or both sides encounter a circular reference
Implementation does not test the [[Prototype]] of objects.
Symbol properties are not compared
WeakMap and WeakSet comparison does not rely on their values

    const assert = require('assert')
console.log(assert.deepEqual({ a: 1 }, { a: 1 }));
// OK
console.log(assert.deepEqual({ a: 1 }, { a: 2 }));
// ERR_ASSERTION

assert.equal()

Tests shallow, coercive equality between the actual and expected parameters using the Abstract Equality Comparison ( == )

  const assert = require('assert')

assert.equal(1, 1);
// OK
assert.equal(1, 2);
// ERR_ASSERTION

assert.notDeepEqual()

Tests for any deep inequality. Opposite of assert.deepEqual().

const assert = require('assert')
assert.notDeepEqual({ a: 1 }, { a: 1 });
// ERR_ASSERTION
assert.notDeepEqual({ a: 1 }, { a: 2 });
// OK

assert.notEqual()

Tests shallow, coercive inequality with the Abstract Equality Comparison (!= ).

const assert = require('assert')
assert.notEqual(1, 1);
// ERR_ASSERTION
assert.notEqual(1, 2);
//  OK