spyOn

What?

Small library for creating spies for your functions and methods in your tests

Why?

Because learn how sinon.js can create spies and implement your own version is great!

How?

With vanilla javascript and some time

Installation

Just add the script lib/spyon.js to your project, or if you are using bower or npm you can also download the package:

• npm:

  $ npm install spyon

• bower:

  $ bower install spyon

Usage and API

spyOn(fn[, context])

spyOn is a function with two parameters, the first one is the function we want to spy on, and the second one is a optional context. That function retuns another function with the samee behaviour of the original function, but it also has some methods to know how many times it has been called and with which arguments.

fn

Type: function

Function we want to spy

context

Type: object

Scope in which fn should be executed

spyOn Methods

getTimesCalled()

returns how many times our function has been called.

getArgsOfCall(callNumber)

returns an array with all the arguments of the nth call (the first call will be indexed by 0).

restore()

returns the original function to restore that function once we have finished spying.

Usage example

To spy on a function, you should override the function you want to spy:

// Start spying on console.log with the console context
console.log = spyOn(console.log, console);
console.log.getTimesCalled(); // 0
 
console.log('Hello world');
console.log.getTimesCalled(); // 1
console.log.getArgsOfCall(0); // ['Hello world']
 
console.log("I'm being spied!!");
console.log.getTimesCalled(); // 2
console.log.getArgsOfCall(1); // ["I'm being spied!!"]
 
// Restore the original function
console.log = console.log.restore();

You can also check the test file to see more details and examples.

License

MIT © Gabriel Perales