chore: Add tests for streamx

[phated]

Closes #55

Blocked on a bug in one of these tests because streamx is causing a "premature close" error in end-of-stream.

cc @mafintosh

[sttk]

@phated This error might be due to streamx.

This error is caused at this position in end-of-stream.

And the following code (using streamx) outputs that stream._writableState.destroyed is undefined though the stream was destroyed.

const streamx = require('streamx');
const stream = streamx.pipeline(
  streamx.Readable.from('foo bar baz'),
  new streamx.Transform({
    transform: function(data, cb) {
      cb(new Error('fail'));
    }
  }),
  new streamx.Writable(),
);
stream.on('error', function(err)  {});
stream.on('close', function(err) {
  console.log('[close]', 'stream.destroyed', stream.destroyed);
  console.log('[close]', 'stream._writableState.destroyed', stream._writableState.destroyed);
});
----
% node test.js    
[close] stream.destroyed true
[close] stream._writableState.destroyed undefined

On the other hand, the following code (using pumpify) outputs that stream._writableState.destroyed is true.

const pumpify = require('pumpify');
const stream = pumpify(
  streamx.Readable.from('foo bar baz'),
  new streamx.Transform({
    transform: function(data, cb) {
      cb(new Error('fail'));
    }
  }),
  new streamx.Writable(),
);
stream.on('error', function(err)  {});
stream.on('close', function(err) {
  console.log('[close]', 'stream.destroyed', stream.destroyed);
  console.log('[close]', 'stream._writableState.destroyed', stream._writableState.destroyed);
});
----
% node test.js 
[close] stream.destroyed true
[close] stream._writableState.destroyed true

Otherwise, end-of-stream should probably look at stream.destroyed instead of stream._readableState.destroyed and stream._writableState.destroyed.

The cause is not stream._writableState.destroy property but stream._writableState.ended or stream.writable property.

[mafintosh]

I poked around your PR to see if this was a streamx issue, but it doesn't seem to be.

Internally you are calling the following in the failing test

eos(stream, { error: false }, callback)

That explicitly disables the error listener in streamx. It therefore doesn't get the "Fail" error, but streamx also doesn't end with the "everything was okay events" ie end/finish, so eos reports an premature close as the it only sees the close event.

This is by design and a good thing. If I missed something let me know.

[sttk]

@mafintosh Certainly, after removing eosConfig = { error: false } to eos, the test case which occured "premature close error" is passed.

@phated Can we remove this eosConfig? Even if it is done, all test cases are passed.

[phated]

@mafintosh thanks for looking into that! I don't exactly remember why I wanted/needed the { error: false } config, but all the tests seem to pass if I remove it (and I got to cleanup a workaround)