Climbing out of the legacy quicksand

Are you working with a legacy application? Whether you inherited it or if the project just grew out of proportion over the years it can be daunting. The thought of making changes or bug fixing can be enough to give you nightmares. No fear you can take a sigh of relief. All is not lost.

A few years ago I found myself working on a legacy project. It wasn't pretty. It was very challenging but I made it through.

And when the next project and the next one and the next and the one after that were also legacy systems, I soon found it much easier to work on them by being more methodical.

Transcript

1. Climbing out of the legacy quicksand Antonis Pavlakis @pavlakis | pavlakis.uk PHP East Midlands December 2016 @PHPem
2. What is legacy ?
3. “Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer technology. ” –Wikipedia (1/3) https://en.wikipedia.org/wiki/Legacy_code
4. “…source code inherited from someone else…” –Wikipedia (2/3) https://en.wikipedia.org/wiki/Legacy_code
5. “… source code inherited from an older version of the software.…” –Wikipedia (3/3) https://en.wikipedia.org/wiki/Legacy_code
6. And can also be… * Insecure, * difficult to read, * difficult to test, * hard to maintain, * spaghetti code, * etc…
7. Some positives… It’s been tried and tested Users know how it works Users are aware of the quirks and workarounds
8. Let’s get started…
9. This talk is about… TDD
10. This talk is about… TDD
11. This talk is about… TRR ?
12. T est
13. Refactor
14. Repeat
15. TDD done backwards?
16. But… Legacy?!!
17. Source: https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-content/images/Doctor-Strange-T railer-breakdown-6.png
18. Let’s look at an example
19. Example #1 - Authentication Enter some information Submit a form
20. Example #1 - Authentication Queries the Database Returns a result
21. Example #1 - Authentication Inputs Application Outputs
22. Black Box T esting
23. Vagrant or Docker ? I still use Vagrant But… it doesn’t really matter.
24. Development Environment If using Vagrant Have a custom box Use provisioning just for the application Expose Database port Enable MySQL logging
25. Expose DB port Edit /etc/my.cnf in the VM and within the [mysqld] section, add: bind-address = 0.0.0.0
26. Expose DB port Give DB user privileges to access DB from anywhere: use mysql; update user set host='%' where user=‘app_user' and host='127.0.0.1'; flush privileges;
27. Expose DB port Add port forwarding to Vagrantfile config.vm.network "forwarded_port", guest: 3306, host: 3306, auto_correct: true
28. Enable MySQL logging general_log = 1 general_log_file = /vagrant/mysql.log Edit /etc/my.cnf in the VM and within the [mysqld] section, add:
29. T esting Environment Can be a separate box
30. T esting environment A lightweight environment (Vagrant, Docker, OS native) Initially we just need PHP (so can use latest version)
31. T ools
32. A php framework for autotesting your business expectations. http://behat.org/en/latest/
33. T est behaviour Complete fields Submit form Check database T est response
34. Checking the Database Can use a shell script Call it through Behat
35. DB Shell Script
36. Checking the Database
37. Example #1 T ests Passed! ✅
38. Refactor
39. Xdebug is your friend
40. Dependency Injection Container
41. DIC Get DB Get Request object Get customer authentication model Get Authentication service
42. DIC $di = new My_App_DiContainer(); $auth = $di->get(‘customer.auth’); $auth = (new \My\App\DiContainer)->get(‘customer.auth’);
43. Example #1 T ests Passed! ✅
44. Autoloading…
45. Composer Compatibility: PHP 5.3.2 PHP 5.3 release date: 30 June 2009
46. Composer composer install --optimize-autoloader
47. Git
48. Composer using Git
49. Decouple all the things
50. DRY? I don’t mind Do Repeat Yourself
51. Start Fresh!
52. Only for this feature
53. BDD Time (yes, we’re still doing TDD)
54. Domain Knowledge Understanding the system… (we’re still on Example #1)
55. Information gathering…
56. What do we need to know? Do users have different roles? What happens if … Login fails User forgets their password …
57. What do we need to know? Do users have different roles? We have two types of users. Customers and Staff members What happens if … Login fails A Customer’s account will lock for 5 minutes if they enter a wrong password more than 3 times. User forgets their password - A Customer can reset their password
58. Ubiquitous language Identify the terminology the Users use Use the same language/terminology the user (or client) uses to describe the system
59. Keep asking questions
60. Domain Knowledge Understand what the feature was designed to do How it is supposed to work How it actually works Any special quirks or edge cases
61. Create a new application
62. Write Unit T ests! 100% T est Coverage!
63. T est Ensure initial Behat tests still pass!
64. Example #1 T ests Passed! ✅
65. Resources Modernizing Legacy Applications in PHP - https:// leanpub.com/mlaphp T est Legacy apps with Behat - https:// speakerdeck.com/agpavlakis/test-legacy-apps- with-behat DB Shell Script - https://github.com/pavlakis/ phpnw15-behat-tutorial/blob/scripts/scripts/db.sh
66. Resources Unglue all the things - https://beau.io/talks/ 2016/09/16/unglue-all-the-things-symfony- live-london-2016 mysql_* to mysqli_* conversion - https:// github.com/philip/MySQLConverterT ool
67. Thanks! @pavlakis | pavlakis.uk https://joind.in/talk/33e19