renderShallow

A utility for shallow rendering React components in tests.

Installation

It's available on npm as render-shallow, so you can run:

npm install --save render-shallow

Usage

renderShallow shallow renders a React element, using React's ShallowRenderer test utility. It wraps the renderer creation, and returns the rendered component, along with some helpers to rerender the element, should it change.

API

renderShallow

// import renderShallow from 'render-shallow'
// or:
// const renderShallow = require('render-shallow')
 
renderShallow(element ReactElement, context ReactContext[Object, optional])
 
returns: Object { output ReactElement, rerender function, rerenderElement function, instance function }

More on React's context.

.output

The React element returned by the shallow renderer.

rerender

rerender()
 
returns: React element

Function that gets the rendered output again. Useful for when a component's state has changed and the DOM should be updated.

rerenderElement

rerenderElement(newElement ReactElement, context Object[optional. Uses initial context, if specified])

Function that renders newElement with the same render instance that renderShallow used. If context was initially specified, that will be reused, otherwise you can supply it. Useful for when you want to tests a props update to your component.

instance

instance()
 
returns: Element instance

Function that gets the mounted instance of the element. Useful if you want to check or use instance state or lifecycle methods.

Example

  // if you just want the shallow-renderer component
  const component = renderShallow(<AReactComponent />).output
 
  // if you want to rerender
  const { output, rerender } = renderShallow(<AReactComponent />)
 
  // if you want to rerender the element
  const { output, rerenderElement } = renderShallow(<AReactComponent />)
 
  // if you want the component's instance
  const { instance } = renderShallow(<AReactComponent />)

Why

I found that in most of the React component tests I wrote, I simply wanted a shallow rendered component to test. The ShallowRenderer API is a little verbose, between the creation and the getting of the output. So I started abstracting that (the .output returned from renderShallow). When I found myself wanting to rerender the component, either because of state or props changes, I added the ability to both re-fetch the output (rerender), or render the element again with new props (rerenderElement). Some time later, when I wanted to test a lifecycle method not part of the shallow render lifecycle, I added instance() so I could call the lifecycle hook directly on the element instance.

Development

• npm run compile - Builds a distributable version of the project

• npm start - Runs tests and reruns on file change

• npm test - Runs tests once

• npm lint - Lints javascript