Add tests to check the order of torrent events

[alxhotel]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update
[ ] Bug fix
[ ] New feature
[X] Other, please explain: Tests

What changes did you make? (Give an overview)

This PR adds tests for #1737

Is there anything you'd like reviewers to focus on?

[feross]

This is excellent! Thanks!!

[alxhotel]

I just realised that the build fails because the tests don't pass in the browser, although I'm not sure why the browser tests weren't executed in the PR checks...

Anyhow, this line does not work in the browser (obviously):

webtorrent/test/torrent-events.js

Line 29 in 84fb338

torrent.addPeer('127.0.0.1:' + client2.address().port)

And it must be moved inside the infoHash handler.

I guess there are two options:

1. Move the test file to the node folder. And only check the order of events in Node.
2. Create a way to add a WebRTC peer to the torrent with: torrent.addPeer(webrtcPeer). There's an issue (#1574) about how to do this manually. But I'm not sure if the implementation shown there is the proper way to do it.

This brings me to another question: why aren't there any tests for downloading and seeding in the browser? Or am I missing something?

[feross]

A lot of the tests are node-only. I think we can solve this by moving the test to the node folder for now. This is still a lot better than not having this test. We can figure out how to solve the webtrc peer issue separately.

We don't run the browser tests in PRs since there is a secret API keys required to interact with Saucelabs and travis doesn't expose those environment variables to PRs since then anyone could send a PR and just log out the secret API key. It's not ideal, but it makes some sense.

[alxhotel]

We don't run the browser tests in PRs since there is a secret API keys required to interact with Saucelabs and travis doesn't expose those environment variables to PRs since then anyone could send a PR and just log out the secret API key. It's not ideal, but it makes some sense.

Ah got it 👍

We can figure out how to solve the webtrc peer issue separately.

Great!

I think we can solve this by moving the test to the node folder for now

Thanks for fixing this 😊