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
   

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2. What is legacy ?
   

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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
   

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4. “…source code inherited from someone else…”
   –Wikipedia (2/3)
   https://en.wikipedia.org/wiki/Legacy_code
   

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5. “… source code inherited from an older version
   of the software.…”
   –Wikipedia (3/3)
   https://en.wikipedia.org/wiki/Legacy_code
   

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6. And can also be…
   * Insecure,
   * difficult to read,
   * difficult to test,
   * hard to maintain,
   * spaghetti code,
   * etc…
   

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7. Some positives…
   It’s been tried and tested
   Users know how it works
   Users are aware of the quirks and
   workarounds
   

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8. Let’s get started…
   

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9. This talk is about…
   TDD
   

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10. This talk is about…
    TDD
    

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11. This talk is about…
    TRR ?
    

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12. T
    est
    

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13. Refactor
    

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14. Repeat
    

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15. TDD
    done backwards?
    

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16. But… Legacy?!!
    

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17. Source: https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-content/images/Doctor-Strange-T
    railer-breakdown-6.png
    

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18. Let’s look at an example
    

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19. Example #1 - Authentication
    Enter some information
    Submit a form
    

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20. Example #1 - Authentication
    Queries the Database
    Returns a result
    

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21. Example #1 - Authentication
    Inputs
    Application
    Outputs
    

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22. Black Box
    T
    esting
    

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23. Vagrant or Docker ?
    I still use Vagrant
    But… it doesn’t really matter.
    

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24. Development Environment
    If using Vagrant
    Have a custom box
    Use provisioning just for the application
    Expose Database port
    Enable MySQL logging
    

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25. Expose DB port
    Edit /etc/my.cnf in the VM and within the [mysqld]
    section, add:
    bind-address = 0.0.0.0
    

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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;
    

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27. Expose DB port
    Add port forwarding to Vagrantfile
    config.vm.network "forwarded_port",
    guest: 3306, host: 3306, auto_correct: true
    

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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:
    

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29. T
    esting Environment
    Can be a separate box
    

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30. T
    esting environment
    A lightweight environment (Vagrant, Docker,
    OS native)
    Initially we just need PHP (so can use latest
    version)
    

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31. T
    ools
    

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32. A php framework for autotesting your business
    expectations.
    http://behat.org/en/latest/
    

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33. T
    est behaviour
    Complete fields
    Submit form
    Check database
    T
    est response
    

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34. Checking the Database
    Can use a shell script
    Call it through Behat
    

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35. DB Shell Script
    

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36. Checking the Database
    

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37. Example #1
    T
    ests Passed! ✅
    

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38. Refactor
    

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39. Xdebug is your friend
    

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40. Dependency Injection
    Container
    

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41. DIC
    Get DB
    Get Request object
    Get customer authentication model
    Get Authentication service
    

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42. DIC
    $di = new My_App_DiContainer();
    $auth = $di->get(‘customer.auth’);
    $auth = (new \My\App\DiContainer)->get(‘customer.auth’);
    

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43. Example #1
    T
    ests Passed! ✅
    

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44. Autoloading…
    

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45. Composer
    Compatibility: PHP 5.3.2
    PHP 5.3 release date: 30 June 2009
    

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46. Composer
    composer install --optimize-autoloader
    

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47. Git
    

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48. Composer using Git
    

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49. Decouple all the things
    

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50. DRY?
    I don’t mind
    Do Repeat Yourself
    

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51. Start Fresh!
    

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52. Only for this feature
    

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53. BDD Time
    (yes, we’re still doing TDD)
    

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54. Domain Knowledge
    Understanding the system…
    (we’re still on Example #1)
    

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55. Information gathering…
    

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56. What do we need to know?
    Do users have different roles?
    What happens if …
    Login fails
    User forgets their password
    …
    

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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
    

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58. Ubiquitous language
    Identify the terminology the Users use
    Use the same language/terminology the user
    (or client) uses to describe the system
    

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59. Keep asking questions
    

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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
    

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61. Create a new application
    

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62. Write Unit T
    ests!
    100% T
    est Coverage!
    

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63. T
    est
    Ensure initial Behat tests still pass!
    

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64. Example #1
    T
    ests Passed! ✅
    

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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
    

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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
    

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67. Thanks!
    @pavlakis | pavlakis.uk
    https://joind.in/talk/33e19
    

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