Measuring Your Code

Measuring your code A talk by Nate Abele @nateabele nate.abele@gmail.com

Confession

Coercion, red bars & broken windows

Continuous

Goal: Perfection

Or at the least, continuous improvement

a.k.a. (kaizen)

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”

Wherefore... (WTF) ?

“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

What can we measure?

Code!!

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

Metric examples

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

Measuring code coverage

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

Measuring documentation coverage Check it out: http://thechaw.com/api_generator A series of rules Assigns weights based on docblock content and various docblock tags

Measuring documentation coverage 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

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

Case study

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 CakePHP Inspector class CakePHP Parser class Based on the awesome work of Sean Coates http://github.com/scoates/tokalizer

Finding things to measure

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

High-level refactoring tools

Can “good code” be quantified??

Good vs. good enough vs. the economy

Measuring Your Code

by Nate Abele on Oct 12, 2009

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