Jest: handle stdout/stderr from the tests

[aaronabramov]

right now whenever something is printed from within a test it's pretty random and breaks the output (esp if you're using json output format)

I think it'd be cool to wrap console.* methods and format the output. eg.

it('...', => {
  console.log('1234566');
  console.warn('111');
  console.error('222');
});

[log: myTest.js] 12334566
[warn: myTest.js] 111
[error: myTest.js] 222

[cpojer]

1435

done.

[okonet]

It seems this breaks modules that help test console output like https://www.npmjs.com/package/test-console or https://github.com/sindresorhus/hook-std

Any idea how to test console output from Jest?

[okonet]

RE: It seems that running with --verbose solved this for me

[cpojer]

console.log = jest.fn();

and then treat it like any other mock.

[okonet]

Thanks @cpojer that worked like a charm!

[G-Rath]

@cpojer while it works, I don't think it's the most ideal solution, as you lose the callsite:

console.log node_modules/jest-mock/build/index.js:480
      resource "aws_route53_zone" "my_zone_com" {}

And you have to test for the parameters that were passed, which is not ideal:

let consoleLogSpy = jest.spyOn(console, 'log');

it('prints the file name', async () => {
  await AwsRoute53Zone.run([zoneId]);

  expect(consoleLogSpy).toHaveBeenCalledWith(
   "resource",
    expect.stringContaining('aws_route53_zone'),
    expect.stringContaining('route_my_zone_com'),
    JSON.stringify({})
  );
});

Would it be feasible to entertain the idea of having some form of expect.stdin & expect.stdout properties that can be used mid-test to test the input & output, seperate from the --verbose/silent flags?

(Personally I'm interested in the output, but figure it would make sense to have stdin too).

Effectively what I'm after is access to the underlying BufferedConsole.