Uncaught ValidationError; mongoose and mocha - node.js

Question

I have an instance method on a mongoose schema, and I cannot catch errors it throws with mocha.
The method does not throw, it calls back with error as param, but mocha test doesn't catch that and I get an uncaught error.
Here's an example module, using mongoose to just do something as a method:
var mongoose = require('mongoose');
var model;
function init(callback) {
mongoose.connect('localhost/test', function() {
var schema = new mongoose.Schema({
a: String
});
schema.methods.act = function(param, cb) {
if (!param) {
console.log('Failing, no param.');
return cb(new Error('Text'));
}
this.a = param;
this.save(cb);
};
model = mongoose.model('schema', schema);
callback();
});
}
function run(cb) {
var instance = new model();
instance.save(function(err) {
if (err) {
throw err;
}
instance.act(null, function(err) {
if (err) {
console.log('An error:', err);
cb(err);
};
});
});
}
module.exports = {
init: init,
run: run
};
Here's a simplified mocha tester:
require('should');
var myModule = require('./testm');
describe('test', function() {
before(function(done) {
// prep stuff
myModule.init(done);
});
it('should catch the error', function(done) {
myModule.run(function(err) {
console.log('Error here:', err);
err.message.should.equal('Text');
done();
});
});
});
Running the test doesn't work as expected:
mocha test
test
Failing, no param.
An error: [Error: Text]
Error here: [Error: Text] Text
1) should catch the error
0 passing (30ms)
1 failing
1) test should catch the error:
Uncaught TypeError: Cannot call method 'equal' of undefined
at /home/zlatko/tmp/test.js:14:26
at /home/zlatko/tmp/testm.js:35:9
at model.schema.methods.act (/home/zlatko/tmp/testm.js:14:16)
at Promise.<anonymous> (/home/zlatko/tmp/testm.js:31:14)
at Promise.<anonymous> (/home/zlatko/tmp/node_modules/mongoose/node_modules/mpromise/lib/promise.js:177:8)
at Promise.emit (events.js:98:17)
at Promise.emit (/home/zlatko/tmp/node_modules/mongoose/node_modules/mpromise/lib/promise.js:84:38)
at Promise.fulfill (/home/zlatko/tmp/node_modules/mongoose/node_modules/mpromise/lib/promise.js:97:20)
at handleSave (/home/zlatko/tmp/node_modules/mongoose/lib/model.js:133:13)
at /home/zlatko/tmp/node_modules/mongoose/lib/utils.js:408:16
at /home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/collection/core.js:128:9
at /home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:1195:7
at /home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:1903:9
at Server.Base._callHandler (/home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/base.js:453:41)
at /home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:487:18
at MongoReply.parseBody (/home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/responses/mongo_reply.js:68:5)
at null.<anonymous> (/home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:445:20)
at emit (events.js:95:17)
at null.<anonymous> (/home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection_pool.js:207:13)
at emit (events.js:98:17)
at Socket.<anonymous> (/home/zlatko/tmp/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection.js:440:22)
at Socket.emit (events.js:95:17)
at Socket.<anonymous> (_stream_readable.js:765:14)
at Socket.emit (events.js:92:17)
at emitReadable_ (_stream_readable.js:427:10)
at emitReadable (_stream_readable.js:423:5)
at readableAddChunk (_stream_readable.js:166:9)
at Socket.Readable.push (_stream_readable.js:128:10)
at TCP.onread (net.js:529:21)
What can I be doing wrong?
Update: changed to be more clear.

Answer 1

In my opinion, #Louis answer is the best way to check for an error in asynchronous scenarios: just assert if it exists, their types and so on.
But, if you really want to throw an error when you receive it in your callback, you can do it with chai-as-promised, like:
it('should catch the error', function() {
return Promise.resolve(function () {
myModule.run(function(err) {
if (err) {throw err;}
});
}).should.eventually.throw(Error);
});
In my example, I'm using should.js as the assertion library, but you can use whatever assertion library you want.