React Stub

A stubbing tool that leads to safer and more maintainable React unit tests.

How it works

You create a stub component out of a real component. The stub is just a normal React component -- you can render it, nest it, inspect its properties, do whatever you want. Example:

// Pretend this is something in your app:
import Login from 'components/login';

import reactStub from 'react-stub';
let LoginStub = reactStub(Login);

Install

npm install --save-dev react-stub

Requirements

• Your app needs to be using React 0.14 or greater (until issue 2 is resolved).

Safer and more maintainable tests

Stubs and mocks are generally risky in dynamic languages such as JavaScript because you have to keep track of interface refactoring in your head and that's hard. This leads to a maintainance burden and in the worst case scenario you might have a passing test suite yet a failing application. React Stub attempts to solve these problems.

Here is an overview of error feedback you get when running tests:

• If the component you've stubbed out gets moved or renamed, you'll see an error.
• If you try to set a property on the stub that isn't in the real component's PropTypes then you'll get an error.
• If you assign an invalid property value on the stub component you'll see a PropTypes validation error.
• If a component forgets to declare a required property on a stubbed sub-component, you'll also see a PropTypes validation error.

Make sure your app uses components correctly

A good case for stubbed components is when you have one component that depends on another but you want to unit test each of them independently. Stubbing out the one you're not testing helps you focus on the interface of the dependent component, which is typically its properties. This also helps keep your test suite lean and fast.

Imagine you have an App component that relies on a Login component. If you want to test App in isolation, the first thing you need to do is re-design your App class to accept a stubbed dependency:

import React, { Component, PropTypes } from 'react';

// Import the real component for reference.
import DefaultLogin from 'components/login';

export default class App extends Component {
  static propTypes = {
    Login: PropTypes.func.isRequired,
  }
  static defaultProps = {
    // When not testing, the real Login is used.
    Login: DefaultLogin,
  }
  render() {
    let Login = this.props.Login;
    return <Login/>;
  }
}

This component design allows you to inject a stub component while testing, like this:

// Pretend these are custom components for your app.
import App from 'components/app';
import Login from 'components/login';

import ReactTestUtils from 'react-addons-test-utils';
import reactStub from 'react-stub';

let LoginStub = reactStub(Login);
ReactTestUtils.renderIntoDocument(
  <App Login={LoginStub} />
);

If the stub gets used incorrectly, you'll see an exception when the top level component gets rendered. For example, if you pass an unexpected attribute, you'll see an error:

ReactTestUtils.renderIntoDocument(
  <LoginStub userId={321} />
);

...
reactStub:Login does not accept property userId

Deeper property inspection

If you want to go beyond simply verifying the PropTypes of the stubbed component, you can use typical React testing approaches. For example:

// Pretend these are custom components for your app.
import App from 'components/app';
import Login from 'components/login';

import ReactTestUtils from 'react-addons-test-utils';
import reactStub from 'react-stub';

let LoginStub = reactStub(Login);
let renderedApp = ReactTestUtils.renderIntoDocument(
  <App Login={LoginStub} />
);

let renderedLogin = ReactTestUtils.findRenderedComponentWithType(
  renderedApp, LoginStub
);

// You could now make assertions about `renderedLogin.props` ...

Development

Clone the source, install NodeJS, and run this from the source directory to install the dependency modules:

npm install

Make sure you have grunt installed and on your path. Otherwise, run this:

npm install -g grunt

To run the tests each time you edit a file, run:

grunt watch-test

To run a test suite once, run:

grunt test

To check for lint errors, run:

grunt eslint

To build a distribution from source, run:

grunt build

Distribution

To create a new release:

• Increment the version in package.json.
• Make sure the release history section in README.md is up to date.
• Commit and push your changes.
• Tag the version (like git tag 0.0.1) and push the tag with git push --tags.
• Run grunt build to create a common JS distribution (in the dist folder).
• Run npm publish.

Release history

• 0.0.2 (2015-12-14)

  • Provide a proper common JS distribution, i.e. no transpilation required.

• 0.0.1 (2015-12-14)

  • Initial release!