How to Test if a Given Value is a React.js Component

2024 Update: Some links to external content are unfortunately outdated. The content in this post doesn't seem relevant to me anymore, except for archival reasons, so I'm not going to update those broken links.

It may seem trivial, but it's a bit tricky to test for that. The documentation for React's Test Utils¹ is lacking examples (as of the time of writing).

By comparing it with Virtual DOM glossary² one can assume that instantiating it with new keyword and then checking with TestUtils.isCompositeComponent is a way to go.

That's how I do it in CoffeScript:

it "is a react component", ->
  # ReactComponents can be instantiated with new keyword for test purposes
  # See https://facebook.github.io/react/docs/glossary.html#react-components
  expect (TestUtils.isCompositeComponent new CheckboxSelect)
    .to.be.ok