Perform code review inside your development team

Rodrigo Aguilera - @marinero

Who am I?

Rodrigo Aguilera

Drupal developer at Ymbra


Pedro Cambra




  • Reduces defects
  • Spreads code ownership
  • Mentors new developers
  • Changed my life as a developer

"But nobody does code review..."

"But nobody does code review..."

  • Too busy to review
  • Code reviews can get nasty
  • Introduces a block
  • I don't want to leave the IDE
  • A cost effective solution
  • Is all about code quality

What am I talking about?

Systematic review of code by your peer developer.

Code review as a firewall.

Be prepared

Be prepared

  • Try to make everything code
  • Review everything: configuration, file names, variable naming...
  • If it can be diffed it can be reviewed
  • The review should ignore all those files not relevant like images, binaries or intermediate code(e.g. sass)

A change in the team culture

A change in the team culture

  • The code is going to be read
  • Make code activity visible
  • Make code digestible (encourage small changes)
  • Support conversations about code

A change in the team culture

  • The best time to talk about parts of the application you don't like
  • Code ownership
  • Be proud about your team not your code
  • Transmission of code and solutions automagically
  • Make code shareable with links
  • You have a proccess in place when you are not sure about changes
  • Multi functional teams

New developers

New developers

  • They will gain experience faster
  • Is much more safer for them to commit code
  • Developers are eager to fix the feedback and reach an agreement

How to get started

  • Go slow
  • Just the diffs
  • Review just the scary smelly parts
  • On demand

Pre/Post commit review

Pre commit is the most interesting
and what most of tools do.

Post commit is also known as code audit or inspection.

Code review by machines

Code Review by machines

Integration with static analysis tools

  • Coding standards
  • Unit test execution
  • Automated builds with continous integration
  • PMD Mess detector, Duplicate code

Code review by humans

Code review by humans

  • Requirements
  • Architecture
  • Futureproof code
  • Coding idioms
  • Potential reuse
  • Domain knowledge

Pair programming

Pair programming

Another kind of code review

  • Real time
  • Very effective and great for mentoring
  • Requires two developers in the same location
  • Less value for the rest of the team

If you don't do code review

If you don't do code review

  • Code ends up being very "personal"
  • No full picture of the project
  • Code that has never been looked at
  • Useless blaming or no one is responsible for the code
  • Monster code
  • Bad code might remain in this condition forever
  • No code reuse
  • Members of the team find it hard to improve skills in the code writing craft

Tool assisted code review

  • Manages workflow and notifications
  • Records of discussion
  • Asyncronous
  • Some are very opinionated
  • Minimum requirements: diffs, inline comments and states
  • Extras: roles, auto merge, commit, rebase, notifications, integration with other tools, etc.


  • Good ol' patches (
  • Pull requests (merge requests in gitlab)
  • Gerrit
  • Redmine patches

Big free software projects (vim and the linux kernel) use it. patches - Dreditor to the rescue

Helps us comment on the patches

Also adds a link to

Github pull requests (merge request on gitlab)

  • Merge the code from one branch to another
  • Can span many commits
  • Some developers prefer this way over d.o

Github pull requests


Web based git review system written in java


Big projects using it
  • Android
  • Cyanogenmod
  • Wikimedia
  • Openstack
  • ChromeOS
  • And many other google projects
  • Gerrit itself

Gerrit list of changes

Gerrit - a changeset

Gerrit diff

Gerrit approval

Gerrit automatic votes

Gerrit - developer side tools


Gerrit drawbacks

  • Interface
  • Has a learning curve
  • Requires to define a review process
  • No audit (Post commit)

Redmine code review

  • Implemented as a plugin
  • Post-commit
  • Creates review request over a commit on demand
  • Or you can inspect the repo creating comments that are issues to be solved

Other tools

  • Differential (Phabricator suite) - PHP

Ego free reviews

Ego free reviews

  • No finger-pointing
  • No point scoring. It's all about doing things right.
  • Don't be pedantic
  • Find problems, not solutions
  • Embrace feedback

Is not that difficult

Now your code review:

Tell me your experience