Assert errors

[gagle]

How can we check that an error must not exist but if it exists, throw the error? This is for asynchronous functions. Right now I do:

var expect = code.expect;
it('foo', function(done) {
  foo(function (err) {
    expect(err).to.not.exist();
    done()
  });
});

But when the function returns an error, lab just tells that err exists when it should not, the stacktrace of the error is not printed.

I'd like to have a function with the identical behaviour of node's built-in assert.ifError(), something like:

var ifError = code.ifError;
it('foo', function(done) {
  foo(function (err) {
    ifError(err); // throws err if err is truthy
    done()
  });
});

[ulrikstrid]

Can't you use something like this?

expect(foo()).not.to.throw(err, 'message');

[gagle]

Nop, foo is asynchronous, it never throws the error, it is returned as an argument.

[AdriVanHoudt]

Hoek.assert(!err, err); ?

[gagle]

hoek.assert() definitely solves the problem but it's not the ideal solution since hoek is a general utilities module, we need something more aligned with code. The implementation of code.ifError() is trivial.

exports.ifError = function (err) {
  if (err) throw err;
}

We can simply use the native function but it'd be good if it is integrated into code:

var assert = require('assert');
it('foo', function(done) {
  foo(function (err) {
    assert.ifError(err);
    done()
  });
});

[AdriVanHoudt]

the reason Code doesn't throw is to continue the tests even if 1 fails. If you want the stack trace of an actual error you can use https://github.com/hapijs/hoek#displaystackslice ?

[gagle]

Well, I need the stack and the error description. If an error occurs I simply want to throw the error.

[ulrikstrid]

Why would you want to throw in your test suite?

[gagle]

To see why expect(err).to.not.exist(); is failing.

[ulrikstrid]

Shouldn't the stacktrace be shown anyway?

[cjihrig]

expect(err).to.not.exist() is the correct thing to do. It will behave like your proposed ifError() method (see below).

> Code = require('code');
{ expect: [Function], incomplete: [Function], count: [Function] }
> expect = Code.expect;
[Function]
> expect(null).to.not.exist();
{ _ref: null, _prefix: '', _location: 'repl:1.1', _flags: {} }
> expect(undefined).to.not.exist();
{ _ref: undefined,
  _prefix: '',
  _location: 'repl:1.8',
  _flags: {} }
> expect(new Error('foo')).to.not.exist();
Error: Expected [Error: foo] to not exist
    at null.<anonymous> (/private/tmp/node_modules/code/lib/index.js:142:17)
    at repl:1:33
    at REPLServer.defaultEval (repl.js:116:27)
    at bound (domain.js:254:14)
    at REPLServer.runBound [as eval] (domain.js:267:12)
    at REPLServer.<anonymous> (repl.js:269:12)
    at emitOne (events.js:77:13)
    at REPLServer.emit (events.js:166:7)
    at REPLServer.Interface._onLine (readline.js:195:10)
    at REPLServer.Interface._line (readline.js:534:8)

[cjihrig]

That's because Lab catches errors so the process does not crash and all of your tests can run. The same behavior should be seen if you explicitly throw an exception.

[lock]

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