Unit Testing and PHP

Robert Ames

Types of testing

• Unit ...
  1 + 1 == 2
• Integation ...
  $lib->balance() == 100.00; $lib->bill( 10 ); $lib->balance() == 110.00;
• Browser ...
  home.php => login.php => checkBalance.php
• Specifications ...
  "When balance due is over $100, no new charges can be accrued."

Why Test?

• Developers add 1 feature per week
• Manual QA tests 10 features per day...

• Automated tests turnaround in seconds or minutes
• Manual QA gives results in hours or days

• Development velocity + quality!

What to test?

• Test risky things
  • Calculations, financial impact, "the purpose" of your program
• Test new things
  • New code is inherently risky
  • Tests at this point serve multiple purposes:
    • Validate your assumptions
    • Define your interface / API
    • Let you know when you're done
    • Oh yeah- you also get repeatable, automated tests
• Test broken things
  • You know... the module that always has bugs reported
• Test core things
  • You know... the module that your business depends on

What not to test?

• Don't test "old" things
  • Odds are they are not risky, broken, or new
  • However, add tests as you find bugs
• Don't test the GUI level (if you can avoid it)
  • Do basic tests, but GUI tests are very hard to keep updated
  • Plus it's at least 10x slower than other options
• Don't test "throwaway code"
  • Testing can increase up-front costs
  • Make sure you'll get a good ROI on your "I"

Why to test?

• Testing improves confidence
• Testing makes you go faster
• Testing tells you when you're done
• Testing makes your code cleaner
• Testing lets you go home earlier
• Tests don't lie

How to test?

• Mmmmmhhh PHP
  • no good answer
• Ideally: PHP4 and PHP5 compatible
  • if not at source level, at least similar interfaces
• Test continuously
  • not once a week
• What works for you
• But KEEP IT SIMPLE!!!!
  • if ( !testFooBar() ) print "FAIL";
  • doesn't need to be more complicated than that

What it looks like...

• results-php4.html
• results-php5.html
• scoringTestAnnotated.html

A Good Test is...

• ...specific
• ...repeatable
• ...quick
• ...independent

Bad Test

function testChargeBad() {
    $x = new BusinessAPI();
    $before = $x->getBalance( 'testUser' );
    $x->addCharge( 'testUser', 10 );
    $after = $x->getBalance( 'testUser' );

    // this duplicates business logic in your test
    assert( 10 == ($after - $before) );
}
    

Better Test

function testChargeBetter() {
    $x = new BusinessAPI();
    $x->setBalance( 'testUser', 100 );
    $x->addCharge( 'testUser', 10 );
    $res = $x->getBalance( 'testUser' );

    // this test is declarative, and can run multiple times
    assert( 110 == $res );
}
    

TDD - Test Driven Development

• Feels "backwards"
• Very Powerful^TM
• Designs a good API
• Get tests for free

TDD - Dominoes

You need to implement a feature

1. Prove that it isn't already implemented.
2. How would you prove that it works?

TDD - Dominoes

• Playing a "5:5" on the board is worth 10 points.
• assert( 10 == $board->play( new Domino(5,5) ) );

TDD - Dominoes

• Can't play a "6:6" after playing a "5:5"
• assert( 10 == $board->play( new Domino(5,5) ) );
• assert( -1 == $board->play( new Domino(6,6) ) );

TDD - Dominoes

• "6:6", "6:4", "4:4" is worth 20 points
• assert( 0 == $board->play( new Domino(6,6) ) );
• assert( 0 == $board->play( new Domino(6,4), "east" ) );
• assert( 20 == $board->play( new Domino(4,4), "east" ) );

TDD - Now write the code

  // the simplest thing to make the
  // tests runnable (some should fail)
  class BOARD {
    function play( $dom )
    {
      return 0;
    }
  }

TDD - Dominoes

• Playing a "5:5" on the board is worth 10 points.
• assert( 10 == $board->play( new Domino(5,5) ) );

TDD - Dominoes

• Can't play a "6:6" after playing a "5:5"
• assert( 10 == $board->play( new Domino(5,5) ) );
• assert( -1 == $board->play( new Domino(6,6) ) );

TDD - Dominoes

• "6:6", "6:4", "4:4" is worth 20 points
• assert( 0 == $board->play( new Domino(6,6) ) );
• assert( 0 == $board->play( new Domino(6,4), "east" ) );
• assert( 20 == $board->play( new Domino(4,4), "east" ) );

TDD - Now write more code

• Playing a "5:5" on the board is worth 10 points.
• assert( 10 == $board->play( new Domino(5,5) ) );

  class BOARD {


    function play( $dom )
    {



    }
  }

Unit Testing

• Often considered an advanced topic
• Unit tests can help anybody
• Not hard to get started

Tactical Goals

In the short term, focus on these:

• Verify a function works properly
• Catch errors quickly (via continuous testing)
• Make changes with confidence

Strategic Goals

Longer term benefits:

• Swap technologies (MySQL → PostgreSQL, PHP4 → PHP5)
• Guaranteed Up-to-date Documentation
• Integrate new developers quicker

Resources

• Pragmatic Project Automation
• Pragmatic Unit Testing (in Java / C#)
  • Very good introduction to Unit Testing
  • Easy to transfer to PHP
• Advanced PHP Programming