How to do custom assertions

How would one go about adding their own, project-local assertions to qunit-dom?

With QUnit, we can say

QUnit.assert.myAssertion = function() {...}

However, to be able to do that with an object returned from QUnit.dom(…), one would have to extend a DOMAssertions object or prototype. I couldn’t seem to find where that is accessible.

[lindem]

Thank you for your response. The problem is not that I don’t know how to write assertions. Also, the example is obviously bad, as people jump in recommending how to solve the particular example rather than what I really asked for.

The problem is that there are things I would have liked to assert on the node directly in a library- or project-specific manner, and I was baffled at the response that it’s just not supported and there are no plans to do so.

Even a generic thing like

assert.dom(selector).satisfies(predicate, "that DOM node satisfies this predicate")

would have been useful. But if I am the only guy who wants extensible DOM assertions I can live with qunit-dom not supporting them.

I did not intend to force the issue or come across as entitled or anything (my schedule is full as well).

Closing, I accept.

[billybonks]

assert.dom('x').hasClass('my-whatever')
assert.dom('x').hasAttribute('data-whatever', 'value')

you could make a helper function

function assertMyTwoThings(selector){
 assert.dom('x').hasClass('my-whatever')
 assert.dom('x').hasAttribute('data-whatever', 'value')
}

or

or you can extend QUnit.assert as @Turbo87 mention

QUnit.extend(QUnit.assert, {
  customDom(selector) {
    return {
       twoThingsAtOnce(){
        //this is not the real way to do the assertion but it will work
         assert.dom(selector).hasClass('my-whatever')
         assert.dom(selector).hasAttribute('data-whatever', 'value')
      }
    }
  },
});

assert.customDom('x').twoThingsAtOnce()

i would just write both assertions but if you really want to do it in one call i recommend the helper function.