This was mostly an oversight in the migration to package:web. In their migration (https://dart.dev/interop/js-interop/package-web#conditional-imports) they state that:

However, since dart:html is deprecated and not supported when compiling to Wasm, the correct alternative now is to use dart.library.js_interop to differentiate between native and web:

This was not done in our initial migration and thus Wasm didn't work properly although the code already can. This PR fixes that and also adjusts the test runner & tests themselves to support this.

One note on the test adjustment: The port returned from the hybrid code that simulates a server accepting Stomp connections comes back as a double in a Wasm environment and this is why we now check the type of the returned port and convert it accordingly.