How to test a custom module running node-fluent-ffmpeg (an async module)?

问题

How do I test a custom module which is simply running a node-fluent-ffmpeg command with Mocha&Chai?

// segment_splicer.js
var config = require('./../config');
var utilities = require('./../utilities');
var ffmpeg = require('fluent-ffmpeg');

module.exports = {
    splice: function(raw_ad_time, crop) {
        if (!raw_ad_time || !crop) throw new Error("!!!!!!!!!! Missing argument");
        console.log("@@@@@ LAST SEGMENT IS BEING SPLITTED.");
        var segment_time = utilities.ten_seconds(raw_ad_time);
        var last_segment_path = config.akamai_user_base + 'segment' + (segment_time + 1) + "_" + config.default_bitrate + "_av-p.ts?sd=10&rebase=on";
        var command = ffmpeg(last_segment_path)
            .on('start', function(commandLine) {
                console.log('@@@@@ COMMAND: ' + commandLine);
            })
            .seekInput('0.000')
            .outputOptions(['-c copy', '-map_metadata 0:s'])
            .duration(crop)
            .on('error', function(err, stdout, stderr) {
                throw new Error('@@@@@ VIDEO COULD NOT BE PROCESSED: ' + err.message);
                console.log('@@@@@ VIDEO COULD NOT BE PROCESSED: ' + err.message);
            })
            .output('public/' + 'segment' + (segment_time + 1) + "_" + config.default_bitrate + "_av-p.ts").run();
    }
}

Here is what I tried:

// test/segment_splicer.js
var expect = require('chai').expect;
var segment_splicer = require('../lib/segment_splicer');


describe('Segment Splicer', function() {
    it('should work', function(done) {
        expect(segment_splicer.splice(1111111, 20)).to.throw(Error);
        done();
    });
});

I get this:

1) Segment Splicer should work: AssertionError: expected undefined to be a function

Because I receive undefined from segment_splicer.spice method.

Thank you!

回答1:

This test should be passing.

A test will only fail if you either assert or expect something in the test which is not true, or if the subject under test throws an uncaught error.

You are not asserting anything in your test, and the only error your subject will throw is if you pass less than 2 arguments, which is not the case in your test.

The ffmpeg method also seems to be asynchronous, which is not compatible with the way you have structured your test.

There are many examples available on setting up async tests, including:

How Mocha Makes Testing Asynchronous JavaScript Processes Fun
Asynchronous Unit Tests With Mocha, Promises, And WinJS
Testing Asynchronous JavaScript

You've gone some way to doing this by referencing the done argument. When this is specified, Mocha will wait until it is called before considering the test finished.

来源：https://stackoverflow.com/questions/29133140/how-to-test-a-custom-module-running-node-fluent-ffmpeg-an-async-module

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javascript

node.js

testing

mocha

chai