• dom-testing-library version: 1.1.0
• node version: N/A
• npm (or yarn) version: N/A

Relevant code or config

https://github.com/kentcdodds/dom-testing-library/blob/f77f943a1887756372993eaf6ee3b054f2f58b91/src/jest-extensions.js#L18-L26

https://github.com/kentcdodds/dom-testing-library/blob/f77f943a1887756372993eaf6ee3b054f2f58b91/src/jest-extensions.js#L63-L85

function checkHtmlElement(htmlElement) {
  if (!(htmlElement instanceof HTMLElement)) {
    throw new Error(
      `The given subject is a ${getDisplayName(
        htmlElement,
      )}, not an HTMLElement`,
    )
  }
}

// ...

const extensions = {
  toBeInTheDOM(received) {
    if (received) {
      checkHtmlElement(received)
    }
    return {
      pass: !!received,
      message: () => {
        const to = this.isNot ? 'not to' : 'to'
        return getMessage(
          matcherHint(
            `${this.isNot ? '.not' : ''}.toBeInTheDOM`,
            'element',
            '',
          ),
          'Expected',
          `element ${to} be present`,
          'Received',
          received,
        )
      },
    }
  },

What you did:

1. Used .toBeInTheDOM() in a test with an element disconnected from the DOM, like here; the test passed, surprisingly.
2. Reviewed the source code of jest-extensions.js

What happened:

Discovered that toBeInTheDOM does not check that the element is attached to a full DOM tree.

Reproduction repository:

This repository's tests.

Problem description:

toBeInTheDOM, according to its name, has to ensure that the given element is in the DOM, i.e. attached to the full DOM tree, not hanging as a standalone element or in a standalone subtree.

Suggested solution:

Find out if the element is actually attached to a DOM document via element.ownerDocument.contains(element), and report an assertion failure if it's not.