Should we leave this `console.log` line? If so, can it be a `console.debug`, maybe with a more informative message? Like `console.debug('Channel Selector - DragMouseDown starting')`
Doesn’t that mean there’s no tests for returning null? I think it might be better to adjust the function to return null if the id is something like “does-not-exist” or equivalent
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This method only returns type `HTMLElement`, and would never return `null`. Should we continue to have `| null` in the type definition if null can't ever be returned?
It would be better if MockIFrame and MockElement were of type HTMLElement, so that you don't need to have `as unknown as HTMLElement` all over the place. Like, you might have to do it in the MockIF...
Is it possible to do something like this:
```ts
const event: Event = {
type: "message",
data: msg,
origin: CHANNEL_SELECTOR_URL,
source,
ports: [connection.port1]
};
parent.dis...
Just flagging this line because `this` scoping is a common pain point in javascript. I think `this` refers to the promise at this point, but could refer to the class...
Either way, please double...