Support use of t.end as callback

[timoxley]

Passing t.end as a callback is a nice feature of tape. It'll end the test & automatically check first arg for an error.

If one wants to use AVA's t.end as a callback though, firstly, it doesn't check for error arg, but secondly it will break due to references to this.

This would provide built-in support for node's errback pattern, echoing AVA's built-in support for promises.

Current implementation:

Test.prototype.end = function () {
    if (this.endCalled) {
        throw new Error('.end() called more than once');
    }

    this.endCalled = true;
    this.exit();
};

https://github.com/sindresorhus/ava/blob/7575ca82855da86e359a4ff8b17bb4588d626e8d/lib/test.js#L137-L144

All AVA Test methods face this issue, perhaps they should all be forcibly bound to the current instance, though t.end is probably by far the most useful one to have bound.

This may be is too much magic though, mainly raising as I noticed this didn't work when migrating my tape tests.

[vadimdemedes]

I like this idea, thank you for submitting it. @sindresorhus what do you think?

[sindresorhus]

Sure, sounds like an easy win.

[timoxley]

perhaps they should all be forcibly bound to the current instance

This could impact people interested in monkeypatching AVA Tests. To maintain some extensibility via clever thisArg trickery, could perhaps do the binding external to the Test constructor e.g. in the Runner

This may not be worth it though as I cannot think of a good use case. Perhaps do this if someone complains.