Measuring Your Code 2.0

Measuring your code
A talk by Nate Abele
@nateabele

nate.abele@gmail.com

Feedback

http://joind.in/1601

Coercion, red bars & broken
windows

Or at the least, continuous
improvement

What people usually think
Estimating costs
Projecting deadlines
Managerial BS!

Client Spec Sheet some paraphrased)
(actual bullet points,
Flash intro with no load time
User account logins, password optional
Ajax chat
“Like Google”

...and my personal favorite

Social network

Measurement is an essential element of
management; there is little chance of
controlling what we can not measure.
- Wikipedia, “Software metric”

“Engineer” & “architect”

Cognitive Dissonance *

Engineers deal with tangible, immutable
constraints, like gravity
The practice of developing software is
an inherently creative discipline
* Thank you, Jones

Cognitive Dissonance
Developer constraints (scope, schedule,
budget) potentially / often in flux
Software is inter-related; working on one
part changes the others
No project is exactly the same as another

Conclusion
It’s not useful to measure high-level,
intangible things like whole projects
This is where scrum comes in handy
Instead, we can use lower-level, more
concrete measurements

More specifically...
Unit test coverage
Complexity
Speed
Documentation

More specifically...

Standards conformance
Refactoration!

Backing up...
What is a metric?
Measurement assigns numbers based on well-
defined meaning

- Sometimes the environment must be
modiﬁed

- Special development procedures that track
various activities - Wikipedia (paraphrased)

You can cheat and use booleans, too

Notes on continuous integration
A build system
Runs on every code commit
Runs tests
Reports

PHP Code Sniffer
PEAR Package:
http://pear.php.net/package/PHP_CodeSniffer

Checks conformance of a set of files against
a series of classes called “sniffs”

PHP Code Sniffer
$ phpcs /path/to/code/myfile.php

FILE: /path/to/code/myfile.php
------------------------------------------------------------------------
FOUND 5 ERROR(S) AFFECTING 2 LINE(S)
------------------------------------------------------------------------
2 | ERROR | Missing file doc comment
47 | ERROR | Line not indented correctly; expected 4 spaces but found 1
51 | ERROR | Missing function doc comment
88 | ERROR | Line not indented correctly; expected 9 spaces but found 6
------------------------------------------------------------------------

PHP Code Sniffer
$ svn commit -m "Test" temp.php
Sending temp.php
Transmitting file data .svn: Commit failed (details follow):
svn: 'pre-commit' hook failed with error output:

FILE: temp.php
--------------------------------------------------------------
FOUND 1 ERROR(S) AND 0 WARNING(S) AFFECTING 1 LINE(S)
--------------------------------------------------------------
2 | ERROR | Missing file doc comment
--------------------------------------------------------------

This is important because things
are standardized

Measuring code complexity
Cyclomatic complexity
Directly measures the number of linearly
independent paths through a program's
source code.
a.k.a. 1 + the number of times it branches

Measuring code complexity
public function render() {
$code = null;

if (isset($this->headers['location']) && $this->status['code'] === 200) {
$code = 302;
}

if (!$status = $this->status($code)) {
throw new Exception('Invalid status code');
}
$this->_writeHeader($status);

foreach ($this->headers as $name => $value) {
$key = strtolower($name);

if ($key == 'location') {
$this->_writeHeader("Location: {$value}", $this->status['code']);
} elseif ($key == 'download') {
$this->_writeHeader('Content-Disposition: attachment; filename="' . $val
} elseif (is_array($value)) {
$this->_writeHeader(
array_map(function($v) use ($name) { return "{$name}: {$v}"; }, $val
);
} elseif (!is_numeric($name)) {
$this->_writeHeader("{$name}: {$value}");
}
}
}

Measuring documentation coverage
Check it out @ http://thechaw.com/api_generator

Check it out:
http://thechaw.com/api_generator

A series of rules
Assigns weights based on docblock content
and various docblock tags

Basic checks:
Do doc tags exist?
Incomplete @param tags?
Do @param tags match actual params?
Does it have a @link to the man page?

Profiling
Get timing / memory usage on every test run
Granular, get statistics per test method
Using continuous integration, code is profiled
on each commit, all on a granular level

CakePHP 1.2 release cycle

1.2 alpha 1.2 beta 1.2 RC1 1.2 RC2 1.2 RC3 1.2 RC4

Metrics are your canary in the coal
mine of your development cycle

By tracking profiler stats (and other metrics),
we can see trends over time, and catch
problems before they become problems

Plus, who doesn’t like pretty graphs?

Finding things to measure
Lithium Inspector class
Lithium Parser class
Based on the awesome work of Sean Coates
http://github.com/scoates/tokalizer

In a dynamic language like PHP, this
is a hard problem.

However, deep code introspection
allows us to ask & answer some
very interesting questions

Project mess detection in PHPUnit

Beyond copy-paste detection & into
pattern recognition

Can “good code” be quantified??

When is “good enough”... good enough?

Incentives and social coercion

Measuring Your Code 2.0

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