reporters should be immune to interference with STDOUT

[boneskull]

Potentially related: #2943

If a reporter uses console.log(), it should retain the function like we do with timers.

This will theoretically allow users to stub out console.log() in their own tests without affecting reporter output.

Since console.log() expects this to be console, it likely needs to take a form of:

const log = console.log.bind(console);

process.stdout.write() may need to be consumed in a similar manner.

To reproduce the problem:

// yuck.spec.js
it('should do, but it do not', function() {
  // user wants to hide output generated by console.log calls in fn 'foo'
  console.log = function() {};
  foo();
});

Another approach would be to instantiate our own Console object (docs) which would bypass the global console entirely. We could consider subclassing Console in order to provide a nice abstraction for reporters consuming process.stdout directly (or other streams).

A workaround (for the user) would be to use something like proxyquire, rewiremock, etc. in lieu of replacing the method outright, like one would with Sinon.

[boneskull]

If possible, ensure this is enforced by ESLint, as we do with the timers.

[plroebuck]

Or more simply, provide the ability to redirect to file.

[boneskull]

I think you’re conflating two separate issues. Even if any reporter could write to a built-in or user-defined stream, that stream would need to be protected from test harness interference.

[craigtaub]

I like the idea of base utility/s to unify reporters and make them more resilient. Happy to have a go when I get time.

[craigtaub]

@boneskull with so many of our reporter tests relying on interfering with process.stdout.write we would have to redo most of them if we did this.
What do you think if we just move the reporters using console.log to use process.stdout.write instead? Very quick change and would add value.

Worth noting console.log calls process.stdout.write internally (with a new-line). And that process.stdout.write cant be stored + used as a reference like console.log can (as it relies on a stream) so not sure how we could do it.
If we tried to make everything use console.log (via reference) we have issues with output (as everything gets a new-line). Tricky.

[boneskull]

@boneskull with so many of our reporter tests relying on interfering with process.stdout.write we would have to redo most of them if we did this.

Can you show how it'd be necessary to change them? I think we can just change the helper function createRunReporterFunction() to spy on calls to process.stdout.write() via a combination of Sinon and rewiremock.

process.stdout.write cant be stored + used as a reference like console.log can

Not sure I understand. console.log (in Node.js) is (likely) bound via Function.prototype.bind to the console object, which is why you can pass log around (this means we'd need to use our own Console instance) as a reference. There's no reason we couldn't do let write = process.stdout.write.bind(process.stdout) if needed.

[boneskull]

I think it'd be helpful to see a proof of concept.

[craigtaub]

I'll put something together

[craigtaub]

Closing as PR was merged.