Install

npm i -D --save-dev magicmock

Prerequisite

Use magicmock with Node.js/io.js (with --harmony_proxies). Currently we only test it against Node.js 4 and Node.js 5. To request more engine support, please kindly send in an issue or pull request.

Usage

Mock method - mockMethod(options)

The terms method and function are interchangeable here.

import {mockMethod} from 'magicmock';

let mockedMethod = mockMethod();
mockedMethod.returnValue = 100;
mockedMethod(1, 2, 3); // => 100
console.log(mockedMethod.called()); // => true
console.log(mockedMethod.calledWith(1, 2, 3)); // => true
console.log(mockedMethod.calledWith(1, 2)); // => false

mockedMethod.returnValue / options.returnValue

Setting returnValue property of the mockedMethod changes the return value when executing mockedMethod.

returnValue is also accepted as an option to mockMethod() factory method.

let mockedMethod = mockMethod({
  returnValue: 100
});
mockedMethod(1, 2, 3); // => 100

options.sideEffect

options.sideEffect allows mockedMethod returns different values depending on side effects from outside world. If sideEffect was defined, returnValue won't not work anymore.

let method = mockMethod({
  sideEffect: [1, 4, 2]
});
method(); // => 1
method(); // => 4
method(); // => 2
method(); // => undefined

It also accepts a mapping function.

let resultMap = {'a': 1, 'b': 2, 'c': 3}
let method = mockMethod({
  sideEffect: (key) => resultMap[key]
});
method('a'); // => 1
method('b'); // => 2
method('c'); // => 3
method('d'); // => undefined

mockedMethod can raise an error defined by options.sideEffect.

let mockedMethod = mockMethod({
  sideEffect: new Error('My GOSH!')
});
mockedMethod(); // => throws error

mockedMethod.callCount()

Returns how many times was the method called.

mockedMethod.called()

Returns a boolean. Indicates whether the method was called or not.

mockedMethod.calledWith(args)

Returns a boolean. Indicates whether the method was called with exactly the same argument list or not.

mockedMethod.getInvocationHistory()

Returns an array of argument lists which mockedMethod was called.

let method = mockMethod();
method();
method(1);
method({a: 1});
method.getInvocationHistory(); // => [[], [1], [{a: 1}]]

Mock object - mockObject(options)

mockObject() factory method creates an object mockedObject. When you access any of undefined property of mockedObject, it returns a mockedMethod instead of undefined.

let mockedObject = mockObject();
// mockedObject.testMethod is undefined
mockedObject.testMethod.returnValue = 101;
console.log(mockedObject.testMethod()); // => 101

You could still assign property value to mockedObject after its creation.

let mockedObject = mockObject();
// mockedObject.testMethod is undefined
mockedObject.testMethod.returnValue = 101;
console.log(mockedObject.testMethod()); // => 101
mockedObject.testMethod = 'not a method anymore';
console.log(mockedObject.testMethod()); // => 'not a method anymore'

mockObject() factory method accepts an option with props key, which defines properties upon creation.

let mockedObject = mockObject({
  props: {
    myProperty: 'this is a string'
  }
});
console.log(mockedObject.myProperty); // => this is a string

Use for testing only

magicmock was designed for testing. You don't want to run magicmock code in production code, neither client-side nor server-side.

If you are using mocha to run test, simply add flag --harmony_proxies. You'd better use some ES6 transpiler like babel.

mocha --compilers js:babel-register --harmony_proxies

License

MIT © tjwudi