Javascript Test - Assertion library

About

assertion in Javascript

Articles Related

Library

• assert module - Node.js’ built-in assert module
• should.js - BDD style
• expect.js - expect() style assertions
• chai - expect(), assert() and should-style assertions
• better-assert - C-style self-documenting assert()
• unexpected - “the extensible BDD assertion toolkit” - used by mocha

They just throws an Error when the assertion is not satisfied.

Devtool Console

Chrome console

function greaterThan(a,b) {
  console.assert(a > b, {"message":"a is not greater than b","a":a,"b":b});
}
greaterThan(5,6);

Implementation Example

• The function to test named plus1

function plus1(a){
    return a + 1;
}

• The test function of the plus1 function

function assertEqual(then, expected) {
    if (result == expected) {
        console.log("The assertion was successful")
    } else {
        console.log("The assertion was not successful. then="+then+", expected="+expected)
    }
}

• The test

var result = plus1(1);
var expectation = 2;
assertEqual(result, expectation);

• The result