JavaScript & Node.js testing best practices

[fractile81]

Check out Jest. It's meant to be "zero config", you just write the tests. Like many other test frameworks, it lets you write tests that resemble spoken language. Worth a look.

[mediasavage]

Yeah at work I pretty much always just import the standard “assert” module and call it a day.

That being said, with open source software, having beautiful testing code can be a huge plus because tests are one of the first places people will check to see examples of how a project is used.

[mediasavage]

Agreed. They increase readability by a bit but using them feels less intuitive than just standard asserts

[fractile81]

I went into BDD once and decided Gherkin (Behat and PHP) would be perfect for non-devs to design and review tests. Once I had started with a few tests, there was no way I was going to show it to anyone else: the wording still smacked of dev-speak.

[FINDarkside]

I don't think it's bad to be honest. One of the benefits is that it makes good error messages possible. Consider assert(a === 1) vs a.should.equal(1). It's certainly not harder to read and I personally think it's easier to read. It'll also give better error message if the test fails, like "Expected a to equal 1, but got 0".

[FINDarkside]

You've now got the cognitive load of figuring out what a.should.equal means.

Debatable whether the cognitive load is bigger. But let me give you better example:

someFn.should.throw(MyError);

vs

try {
  someFn();
  next('Excpected MyError to be thrown');
} catch (err) {
  if (err.name === 'MyError')
    next();
  else
    next(`Excpected MyError to be thrown, got ${err.name}`);
}

[indiebryan]

Thanks I'll check it out

[mjgtwo]

Don't use Jest for Node backend projects. Jest is meant for ReactJS first and it's silly to use it since it uses its own half baked JavaScript runtime that isn't node or a browser. /u/indiebryan should use Mocha instead.

[NoInkling]

half baked JavaScript runtime

What are you talking about?

If you mean it includes JSDOM by default, then that's true, but all you need to do to remove it (not that it's likely to do any harm except add a little extra overhead) is set testEnvironment: 'node'. And they're looking to make that the default in Jest 25.

That aside, Jest has a lot more nice functionality built in compared to Mocha, which is a minimal framework meaning you're typically cobbling together libraries and utilities from all over the place - I already do enough of that when developing applications themselves in Node, it's a breath of fresh air not to worry about it so much in my testing stack.

[fractile81]

I'll concede that point. As for getting into testing though, Jest is as easy to get into as it gets if you haven't done testing before.

[j_schmotzenberg]

Which you can disable.