Allow testing additional error properties with t.throws(Async)

[tommy-mitchell]

Errors can be extended to have additional properties, such as with execa's childProcessResult:

Example of additional error properties

import {execa} from 'execa';

// Catching an error
try {
	execaSync('unknown', ['command']);
} catch (error) {
	console.log(error);
	/*
	{
		message: 'Command failed with ENOENT: unknown command spawnSync unknown ENOENT',
		errno: -2,
		code: 'ENOENT',
		syscall: 'spawnSync unknown',
		path: 'unknown',
		spawnargs: ['command'],
		originalMessage: 'spawnSync unknown ENOENT',
		shortMessage: 'Command failed with ENOENT: unknown command spawnSync unknown ENOENT',
		command: 'unknown command',
		escapedCommand: 'unknown command',
		stdout: '',
		stderr: '',
		failed: true,
		timedOut: false,
		isCanceled: false,
		killed: false,
		cwd: '/path/to/cwd'
	}
	*/
}

Since assertions don't throw (#3201), testing these values requires guarding against undefined and disallows destructuring the return value of t.throws(Async) itself:

const error = t.throwsAsync(execa('node', ['fail.js']));

t.is(error?.exitCode, 1);
t.is(error?.stderr, 'fail');

It'd be much nicer to test these error properties directly:

t.throwsAsync(
	execa('node', ['fail.js']),
	{exitCode: 1, stderr: 'fail'},
);

[sindresorhus]

Since assertions don't throw

This will hopefully change: #3201

[tommy-mitchell]

Whoops, that’s the issue I meant to link.

[novemberborn]

I don't bother with the guards, instead in Typescript I use the ! assertion so the type checker is happy.

[tommy-mitchell]

Fair, I still think it would be nice to test that the thrown error has the given properties in the same assertion.

[novemberborn]

Maybe a like field which follows t.like semantics?