Mockfill

Mockfill aims to make mocking objects in typescript an easier experience. When mocking interfaces in typescript tests, every method must be defined in order to be compiled. Even if you can fix the compiler errors, you still need to mock every method your class under test might use.

Ideally, we want our tests to only mock methods that play a part in what we are testing. Mockfill allows us to do this by filling in missing methods with default implementations.

Under the hood, Mockfill uses the Proxy class to intercept all attempts to get properties from an object. If the underlying object has the property, the Proxy defers to the underlying object. If the object is missing the property, the Proxy supplies a default value.

Installing / Getting started

Install

npm install --save-dev mockfill

Usage

import 'harmony-reflect'
import * as Mockfill from 'mockfill'

interface MyInterface {
   methodOne();
   methodTwo();
}

function test() {
   
   //Create a stubbed implementation of MyInterface for our test.
   const myInstance = {
      //We only care about testing methodOne in this test.
      methodOne() {
         return 1;
      }
   }
   const mock = Mockfill.mock<MyInterface>(myInstance);
   
   mock.methodOne(); //returns 1 as expected.
   mock.methodTwo(); //returns nothing, but does not throw an error!
}

Because Mockfill uses the Proxy object you must do two things when using it.

1. require 'harmony-reflect' once somewhere in your project.
2. run node with the --harmony-proxies option.

Developing

This project requires the typings tool to manage external typescript definition files.

git clone https://github.com/dkellycollins/mockfill.git
cd mockfill/
npm install
cd src/
typings install

Installs project dependencies and typescript definition files.

Building

npm compile

gulp compile

Both commands execute the gulp compile task.

Testing

gulp compile
mocha dist/test/**/* --harmony-proxies

Runs all tests in the compiled test directory.

Contributing

Contributing is more then welcome! Just fork this repo and create a pull request with changes you would like to see.

Licensing

The code in this project is licensed under MIT license.