Streams: tests for teeing readable byte streams

[MattiasBuelens]

See whatwg/streams#1114 for the accompanying spec change.

[domenic]

Generally looks good and quite exhaustive; impressive as always.

Were you able to check coverage on the reference implementation?

[MattiasBuelens]

Were you able to check coverage on the reference implementation?

Riiiight, we have a script for that! 😅 I haven't checked it yet, I'll have a look.

[MattiasBuelens]

Looks like npm run coverage is broken in the reference implementation. 😬

Istanbul works by hooking into require(). Previously, we'd just require() the reference implementation and expose that to jsdom's window in the test runner. But nowadays we bundle the whole thing with Browserify first and then eval the bundle to get it in jsdom's window. Since we're no longer using require(), Istanbul doesn't process any of our code and can't report any coverage.

Not sure if/how we want to fix this? 😕

[MattiasBuelens]

Right, managed to fix the coverage script. Some cases aren't tested yet:

• Pull with a BYOB reader, then pull with a default reader (should swap the internal reader)
• Pull with a default reader, then close the stream while the other branch has a pending BYOB read (should call respond(0))
• Pull with a default reader, then error the stream
• Pull with a BYOB reader, then close the stream while the other branch has a pending BYOB read (should call respond(0))
• Pull multiple times with one reader (should hit the if (reading === true) check in the pull algorithms)

[domenic]

LGTM. Not sure why the bots are failing; try rebasing?

@ricea feel free to take a look