Of course this then fails in ci. Any way to mock out is-ci to return true? Not sure if proxyquire would even work because of the laziness.

Couldn't you just set the NO_UPDATE_NOTIFIER environment variable when running from your CI?

Absolutely, and that's what's probably gonna happen.

With npm@5 using this module though, I'm afraid everybody will get unwanted (and useless info) during CI runs whenever the bundled version of npm in node is not latest (which is the case for node 8 now).

It's a bit special case that it actually breaks Lerna's test suite since they assert on stdout after invoking node.

But I don't really see the use case you'd want the warning on CI.

This needs to be documented.

@sindresorhus I can add docs if we can get around the issue with the tests. Should I mock is-ci? If so, any preferred mocking implementations

Should I mock is-ci? If so, any preferred mocking implementations

Sure, Sinon.js is good.

I wasn't able to mock using sinon as I needed to change the default export.

Ended up going with mock-require

Looks good. Thank you @SimenB :)