bunyan-gt

End to end unit testing using structured logging

This module connects TDD tool QUnit-like runner gt and structured JSON logger bunyan.

example

// index.js
// output structured JSON logging using bunyan
log.debug('message', { foo: 'foo' });
...
 
// test.js
var bgt = require('bunyan-gt');
gt.async('testing index.js', 2, function () {
  // execute index.js inside a unit test and capture bunyan output
  gt.exec('node', ['./index.js', '--debug'], 0,
    function inspectOutput(stdout, stderr) {
      // bunyan output helpers
      var allMessages = bgt(stdout, 'example');
      var messages = bgt(allMessages, 'message');
      // shortcut: bgt(stdout, 'example', 'message')
      gt.equal(messages[0], 'foo');
    });
});

Other logging frameworks or console messages are ignored.

Why?

It is simple to unit test a small piece of code. It is much harder to confirm that a complicated end to end test confirms the expected behavior. It is simple to execute a CLI tool with given inputs and check the exit code, as shown in this post.

On the other hand, a human programmer would check the program's execution by looking at the logs. Human output is hard to parse, so automating this process as part of the unit tests would be hard if we were logging pure text messages. The solution is to output labeled JSON objects, for example using bunyan logging module. They are simple to enable (for example using different logging levels) when needed, simple to parse and easy to query from the unit tests to assert the correct execution.

Bunyan example

Here is a simple program with both console and bunyan logging

var bunyan = require('bunyan');
var log = bunyan.createLogger({ name: 'myapp' });
log.level(process.argv.some(function (str) {
  return str === '--debug';
}) ? 'debug' : 'info');
 
console.log('hi from console');
 
log.debug('message', {
  foo: 'foo',
  bar: 'bar'
});
 
log.debug('message 2', {
  foo: 'foo',
  bar: 'bar'
});

It only outputs bunyan messages if the user ran the program with --debug command line option.

A good way to run the program and see human-formatted output is to install bunyan globally npm install -g bunyan and pipe the program's output

$ node index.js | bunyan -o short
hi from console
03:12:41.848Z  INFO myapp: message { foo: 'foo', bar: 'bar' }
03:12:41.849Z  INFO myapp: message { foo: 'foo', bar: 'bar' }

You can also suppress non-bunyan logging using --strict option

$ node index.js | bunyan --strict -o short
// "hi from console" is hidden

Small print

Author: Gleb Bahmutov © 2014

• @bahmutov
• glebbahmutov.com
• blog

License: MIT - do anything with the code, but don't blame me if it does not work.

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Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

Copyright (c) 2014 Gleb Bahmutov

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.