Legacy Code - Testing & Safe Refactoring

Legacy Code - Testing & Safe Refactoring

"I can't test this code because it's legacy. I need to update the code to make it testable. How can I manage that, without breaking existing functionality? I'll need to write some tests, but... argh!"

We've all been there! In this talk we'll look at safe ways to refactor 'untestable' code to make it testable - without breaking any existing functionality. Promise! Then, further changes will be much easier!

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Katy Ereira

April 13, 2019
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  1. @maccath | Katy Ereira | #PHPYorkshire19 Legacy Code. testing &

    safe refactoring
  2. @maccath | Katy Ereira | #PHPYorkshire19 What is legacy code?

    • Code that wasn’t written by you, just now • Code resulting from incorrect assumptions • Code built using unsupported technology • Code that isn’t tested
  3. @maccath | Katy Ereira | #PHPYorkshire19 What is refactoring? •

    Changing existing code without changing the application logic • Improving code structure • Usually done in small, incremental steps
  4. @maccath | Katy Ereira | #PHPYorkshire19 Why would I refactor?

    • Improve other developer’s understanding • Increase the application’s performance • Introduce new technology • Accommodate changes in product requirements
  5. @maccath | Katy Ereira | #PHPYorkshire19 What is unit testing?

    • Verification that each individual ‘unit’ of an application works as intended • Units are the component parts of your application • Generally, each behaviour is a unit; likely to be contained within a function • Unit testing is not a substitute for other types of testing
  6. @maccath | Katy Ereira | #PHPYorkshire19 Why would I unit

    test? • Aid in the documentation of the system • To prevent regressions when adding/changing code • To test integration with new technology • For validation of product requirements
  7. @maccath | Katy Ereira | #PHPYorkshire19 Paradox: can’t refactor untested

    code, but can’t test the code until it’s refactored.
  8. @maccath | Katy Ereira | #PHPYorkshire19 A solution 1. Rewrite

    the entire codebase 2. … 3. Profit! 1. Rewrite the entire codebase 2. … 3. Profit!
  9. @maccath | Katy Ereira | #PHPYorkshire19 A better solution 1.

    Perform just enough refactoring to make the code testable 2. Test the code 3. Refactor the code further 4. Profit!
  10. @maccath | Katy Ereira | #PHPYorkshire19 Assumptions: you’re developing with

    PHP and you have access to a terminal with Composer.
  11. @maccath | Katy Ereira | #PHPYorkshire19 “ PHPUnit is a

    programmer-oriented testing framework for PHP. It is an instance of the xUnit architecture for unit testing frameworks. PHPUnit Reference: https://phpunit.de/
  12. @maccath | Katy Ereira | #PHPYorkshire19 I’m still on PHP

    version 5.6 / 7.0 / 7.1 ! PHPUnit Version PHP Version Supported Until 9 7.3 Future release 8 7.2 February 5, 2021 7 7.1 February 7, 2020 6 7.0 [unsupported] February 8, 2019 5 5.6 [unsupported] February 2, 2018
  13. @maccath | Katy Ereira | #PHPYorkshire19 Install via Composer: PHPUnit

    - installation $ composer require --dev phpunit/phpunit ^|version| $ ./vendor/bin/phpunit --version PHPUnit x.y.z by Sebastian Bergmann and contributors.
  14. @maccath | Katy Ereira | #PHPYorkshire19 Anatomy of a unit

    test tests/ExampleTest.php class ExampleTest extends PHPUnit\Framework\TestCase { public function testSomeFunction() { $result = someFunction(); // Should return true $this->assertTrue($result); } }
  15. @maccath | Katy Ereira | #PHPYorkshire19 Run your tests: Running

    the tests $ ./vendor/bin/phpunit tests PHPUnit 7.5.8 by Sebastian Bergmann and contributors. . 1 / 1 (100%) Time: 64 ms, Memory: 4.00 MB OK (1 test, 1 assertion)
  16. @maccath | Katy Ereira | #PHPYorkshire19 “ Mockery Mockery is

    a simple yet flexible PHP mock object framework for use in unit testing with PHPUnit, PHPSpec or any other testing framework. Reference: https://github.com/mockery/mockery
  17. @maccath | Katy Ereira | #PHPYorkshire19 Install via Composer: $

    composer require --dev mockery/mockery Mockery - Installation
  18. @maccath | Katy Ereira | #PHPYorkshire19 Mockery - Usage tests/ExampleTest.php

    class ExampleTest extends PHPUnit\Framework\TestCase { public function setUp() { $mockObject = Mockery::mock(Object::class); // Mock object. } }
  19. @maccath | Katy Ereira | #PHPYorkshire19 Mockery - Usage tests/ExampleTest.php

    class ExampleTest extends PHPUnit\Framework\TestCase { public function setUp() { $mockObject = Mockery::mock(Object::class); $mockObject->shouldReceive('method') // Expectation ->once() // Method called once ->andReturn(true); // Method returns true } }
  20. @maccath | Katy Ereira | #PHPYorkshire19 Mockery - Usage tests/ExampleTest.php

    class ExampleTest extends PHPUnit\Framework\TestCase { public function tearDown() { Mockery::close(); // Always close after running tests! } }
  21. @maccath | Katy Ereira | #PHPYorkshire19 Mockery - Usage DO:

    • Mock dependencies, when needed. • Be aware of tautological testing. DON’T: • Mock everything. • Mock the system under test.
  22. @maccath | Katy Ereira | #PHPYorkshire19 Disclaimer: the following examples

    are deliberately simple.
  23. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario #1

    Output interference
  24. @maccath | Katy Ereira | #PHPYorkshire19 A method that echoes

  25. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function yodel($tune =

    null) { if ($tune) { echo $tune; // The yodel is echoed back } else { echo 'Odl lay ee'; // A yodel begins } } A method that echoes
  26. @maccath | Katy Ereira | #PHPYorkshire19 A method that echoes

    tests/YodelTest.php class PrintedOutputTest extends PHPUnit\Framework\TestCase { public function testNewYodel() { yodel(); // Should echo ‘Odl lay ee’ } public function testEchoedYodel() { yodel('Lay hee hoo'); // Should echo ‘Lay hee hoo’ } }
  27. @maccath | Katy Ereira | #PHPYorkshire19 Run your tests: A

    method that echoes $ ./vendor/bin/phpunit tests PHPUnit 7.5.8 by Sebastian Bergmann and contributors. ROdl lay eeR 2 / 2 (100%)Lay hee hoo Time: 60 ms, Memory: 4.00 MB There were 2 risky tests
  28. @maccath | Katy Ereira | #PHPYorkshire19 • Prevent output being

    echoed to the test runner • Capture the output that would otherwise be echoed • Perform assertions on the captured output A method that echoes
  29. @maccath | Katy Ereira | #PHPYorkshire19 tests/YodelTest.php public function testNewYodel()

    { ob_start(); // Start capturing output. yodel(); } A method that echoes
  30. @maccath | Katy Ereira | #PHPYorkshire19 tests/YodelTest.php public function testNewYodel()

    { ob_start(); yodel(); ob_end_clean(); // Finish capturing output. } A method that echoes
  31. @maccath | Katy Ereira | #PHPYorkshire19 tests/YodelTest.php public function testNewYodel()

    { ob_start(); yodel(); $output = ob_get_contents(); // Get the output. ob_end_clean(); } A method that echoes
  32. @maccath | Katy Ereira | #PHPYorkshire19 tests/YodelTest.php public function testNewYodel()

    { ob_start(); yodel(); $output = ob_get_contents(); ob_end_clean(); $this->assertEquals('Odl lay ee', $output); // Success! } A method that echoes
  33. @maccath | Katy Ereira | #PHPYorkshire19 tests/YodelTest.php public function testEchoedYodel()

    { ob_start(); yodel('Lay hee hoo'); $output = ob_get_contents(); ob_end_clean(); $this->assertEquals('Lay hee hoo', $output); // Success! } A method that echoes
  34. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario #2

    Hard-coded dependencies
  35. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

  36. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getPowerLevel() {

    $result = Goku::powerLevel(); // Goku’s power level is static. return $result > 9000 ? "It’s over 9000!" : "Suppressed."; } A static method call
  37. @maccath | Katy Ereira | #PHPYorkshire19 tests/PowerLevelTest.php class PowerLevelTest extends

    PHPUnit\Framework\TestCase { public function testUnder9000() { $result = getPowerLevel(); } public function testOver9000() { $result = getPowerLevel(); } } A static method call
  38. @maccath | Katy Ereira | #PHPYorkshire19 Goku.php class Goku {

    static function powerLevel() { return 5000; // Always returns 5000. } } A static method call
  39. @maccath | Katy Ereira | #PHPYorkshire19 tests/PowerLevelTest.php public function testUnder9000()

    { $result = getPowerLevel(); $this->assertEquals('Suppressed.', $result); // Success! } A static method call
  40. @maccath | Katy Ereira | #PHPYorkshire19 tests/PowerLevelTest.php public function testOver9000()

    { $result = getPowerLevel(); $this->assertEquals('It’s over 9000!', $result); // Failure. } A static method call
  41. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

    • Create a new ‘mock’ of Goku, using a Mockery alias. • Set the return value of Goku::powerLevel to be 9001. • Run tests in separate processes.
  42. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

    tests/PowerLevelTest.php public function testOver9000() { $superSaiyanGoku = Mockery::mock('alias:Goku'); // Mock Goku $result = getPowerLevel(); $this->assertEquals('It’s over 9000!', $result); // Failure. }
  43. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

    tests/PowerLevelTest.php public function testOver9000() { $superSaiyanGoku = Mockery::mock('alias:Goku') ->shouldReceive('powerLevel') // Set Goku’s power level ->andReturn(9001); // to over 9000. . $result = getPowerLevel(); $this->assertEquals('It’s over 9000!', $result); // Failure. }
  44. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

    tests/PowerLevelTest.php /** * @runTestsInSeparateProcesses */ class PowerLevelTest extends PHPUnit\Framework\TestCase { // ... }
  45. @maccath | Katy Ereira | #PHPYorkshire19 A static method call

    tests/PowerLevelTest.php public function testOver9000() { $superSaiyanGoku = Mockery::mock('alias:Goku') ->shouldReceive('powerLevel') ->andReturn(9001); . $result = getPowerLevel(); $this->assertEquals('It’s over 9000!', $result); // Success! }
  46. @maccath | Katy Ereira | #PHPYorkshire19 A hard-coded dependency

  47. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getOutlook() {

    $weather = new WeatherForecast(); // A hard-coded dependency. $outlook = $weather->isSunny() ? "full" : "empty"; return "The glass is half $outlook."; } A hard-coded dependency
  48. @maccath | Katy Ereira | #PHPYorkshire19 WeatherForecast.php class WeatherForecast {

    static function isSunny() { return (bool) rand(0, 1); // Returns random true/false. } } A hard-coded dependency
  49. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php class OutlookTest extends

    PHPUnit\Framework\TestCase { public function testHalfFull() { $result = getOutlook(); } public function testHalfEmpty() { $result = getOutlook(); } } A hard-coded dependency
  50. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php public function testHalfFull()

    { $result = getOutlook(); $this->assertEquals('The glass is half full', $result); } A hard-coded dependency
  51. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php public function testHalfEmpty()

    { $result = getOutlook(); $this->assertEquals('The glass is half empty', $result); } A hard-coded dependency
  52. @maccath | Katy Ereira | #PHPYorkshire19 A hard-coded dependency •

    Mock the WeatherForecast, using a Mockery override. • Set the return value of WeatherForecast::isSunny to be true or false. • Perform assertions based on mocked return values. • Run tests in separate processes.
  53. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $result = getOutlook(); $this->assertEquals('The glass is half full', $result); } A hard-coded dependency
  54. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock('overload:WeatherForecast'); // Overload $result = getOutlook(); $this->assertEquals('The glass is half full', $result); } A hard-coded dependency
  55. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock('overload:WeatherForecast') ->shouldReceive('isSunny'); // Set expectation $result = getOutlook(); $this->assertEquals('The glass is half full', $result); // Success! } A hard-coded dependency
  56. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock('overload:WeatherForecast') ->shouldReceive('isSunny') ->andReturn(true); // Force return value true $result = getOutlook(); $this->assertEquals('The glass is half full', $result); // Success! } A hard-coded dependency
  57. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfEmpty()

    { $mockForecast = Mockery::mock('overload:WeatherForecast') ->shouldReceive('isSunny') ->andReturn(false); // Force return value false $result = getOutlook(); $this->assertEquals('The glass is half empty', $result); // Success! } A hard-coded dependency
  58. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php /** * @runTestsInSeparateProcesses

    */ class OutlookTest extends PHPUnit\Framework\TestCase { // ... } A hard-coded dependency
  59. @maccath | Katy Ereira | #PHPYorkshire19 • Refactor the code

    to use an injected dependency. • Mock the dependency. • Inject the mocked dependency. • Remove @runTestsInSeparateProcesses annotation. Refactoring: hard-coded dependencies
  60. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getOutlook() {

    $weather = new WeatherForecast(); $outlook = $weather->isSunny() ? "full" : "empty"; return "The glass is half $outlook."; } A hard-coded dependency
  61. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getOutlook(WeatherForecast $weather

    = null) // Inject { $weather = new WeatherForecast(); $outlook = $weather->isSunny() ? "full" : "empty"; return "The glass is half $outlook."; } A hard-coded dependency
  62. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getOutlook(WeatherForecast $weather

    = null) { $weather = $weather ?? new WeatherForecast(); // Use injected dependency $outlook = $weather->isSunny() ? "full" : "empty"; return "The glass is half $outlook."; } A hard-coded dependency
  63. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock('overload:WeatherForecast') ->shouldReceive('isSunny') ->andReturn(true); $result = getOutlook(); $this->assertEquals('The glass is half full', $result); // Success! } A hard-coded dependency
  64. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock(WeatherForecast::class) // No overload! ->shouldReceive('isSunny') ->andReturn(true); $result = getOutlook(); $this->assertEquals('The glass is half full', $result); // Success! } A hard-coded dependency
  65. @maccath | Katy Ereira | #PHPYorkshire19 tests\OutlookTest.php public function testHalfFull()

    { $mockForecast = Mockery::mock(WeatherForecast::class) ->shouldReceive('isSunny') ->andReturn(true); $result = getOutlook($mockForecast); // Inject! $this->assertEquals('The glass is half full', $result); // Success! } A hard-coded dependency
  66. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php /** * @runTestsInSeparateProcesses

    */ class OutlookTest extends PHPUnit\Framework\TestCase { // ... } A hard-coded dependency
  67. @maccath | Katy Ereira | #PHPYorkshire19 tests/OutlookTest.php /** * @runTestsInSeparateProcesses

    */ class OutlookTest extends PHPUnit\Framework\TestCase { // ... } A hard-coded dependency
  68. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario #3

    Ungraceful exits
  69. @maccath | Katy Ereira | #PHPYorkshire19 Redirections

  70. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getMeOutOfHere(bool $imACelebrity

    = false) { if ($imACelebrity) { header('Location: http://google.com'); } return "Nope!"; } Redirections
  71. @maccath | Katy Ereira | #PHPYorkshire19 tests\GetMeOutTest.php class GetMeOutTest extends

    PHPUnit\Framework\TestCase { public function testLeaveMeHere() { getMeOutOfHere(); } public function testGetMeOut() { getMeOutOfHere($imACelebrity = true); } } Redirections
  72. @maccath | Katy Ereira | #PHPYorkshire19 tests\GetMeOutTest.php /** * @runTestsInSeparateProcesses

    */ class GetMeOutTest extends PHPUnit\Framework\TestCase { public function testLeaveMeHere() { … } public function testGetMeOut() { … } } Redirections
  73. @maccath | Katy Ereira | #PHPYorkshire19 tests\GetMeOutTest.php public function testLeaveMeHere()

    { $result = getMeOutOfHere(); $this->assertEquals('Nope!', $result); // Success! } Redirections
  74. @maccath | Katy Ereira | #PHPYorkshire19 tests\GetMeOutTest.php public function testGetMeOut()

    { $result = getMeOutOfHere($imACelebrity = true); $this->assertNotEquals('Nope!', $result); // Failure. } Redirections
  75. @maccath | Katy Ereira | #PHPYorkshire19 Refactoring: Redirections • Return/continue/break

    after (potentially) redirecting. or • Set redirection header as the very last step.
  76. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getMeOutOfHere(bool $imACelebrity

    = false) { if ($imACelebrity) { header('Location: http://google.com'); return; // Don’t go any further! } return "Nope!"; } Redirections
  77. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function getMeOutOfHere(bool $imACelebrity

    = false) { if (!$imACelebrity) { return "Nope!"; // Return early. } header('Location: http://google.com'); } Redirections
  78. @maccath | Katy Ereira | #PHPYorkshire19 tests\GetMeOutTest.php public function testGetMeOut()

    { $result = getMeOutOfHere($imACelebrity = true); $this->assertNotEquals('Nope!', $result); // Success! } Redirections
  79. @maccath | Katy Ereira | #PHPYorkshire19 Exiting

  80. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function brexit(bool $remoaner

    = false) { if ($remoaner) { return 'People’s vote!'; } exit; } Exiting
  81. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php class BrexitTest extends

    PHPUnit\Framework\TestCase { public function testBrexit() { $result = brexit(); } public function testRemoaner() { $result = brexit($remoaner = true); } } Exiting
  82. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testRemoaner()

    { $result = brexit($remoaner = true); $this->assertEquals('People’s vote!', $result); // Success! } Exiting
  83. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testBrexit()

    { $result = brexit(); $this->assertEmpty($result); // Never gets here. } Exiting
  84. @maccath | Katy Ereira | #PHPYorkshire19 Refactoring: Exiting • Create

    a wrapper around the exit functionality. • Inject the exit wrapper. • Safely refactor to use the exit wrapper. • Mock the exit wrapper.
  85. @maccath | Katy Ereira | #PHPYorkshire19 BrexitUtility.php class BrexitUtility {

    public function brexitMeansBrexit() { exit; // Completely exits. } } Exiting
  86. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function brexit(bool $remoaner,

    BrexitUtility $brexitUtil = null) // Inject { if ($remoaner) { … } exit; } Exiting
  87. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function brexit(bool $remoaner,

    BrexitUtility $brexitUtil = null) { $brexitUtil = $brexitUtil ?? new BrexitUtility(); // Set default. if ($remoaner) { … } exit; } Exiting
  88. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function brexit(bool $remoaner,

    BrexitUtility $brexitUtil = null) { $brexitUtil = $brexitUtil ?? new BrexitUtility(); if ($remoaner) { … } $brexitUtil->brexitMeansBrexit(); // Use the brexit utility. } Exiting
  89. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testBrexit()

    { $mockBrexitUtil = Mockery::mock(BrexitUtility::class); // Mock Brexit util $result = brexit(); $this->assertNotEquals('People’s vote!', $result); // Failure. } Exiting
  90. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testBrexit()

    { $mockBrexitUtil = Mockery::mock(BrexitUtility::class) ->shouldIgnoreMissing(); // Do nothing... $result = brexit(); $this->assertNotEquals('People’s vote!', $result); // Failure. } Exiting
  91. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testBrexit()

    { $mockBrexitUtil = Mockery::mock(BrexitUtility::class) ->shouldIgnoreMissing(); $result = brexit($remoaner = false, $mockBrexitUtil); // Use it. $this->assertNotEquals('People’s vote!', $result); // Success! } Exiting
  92. @maccath | Katy Ereira | #PHPYorkshire19 tests\BrexitTest.php public function testBrexit()

    { $mockBrexitUtil = Mockery::mock(BrexitUtility::class) ->shouldIgnoreMissing(); $result = brexit($remoaner = false, $mockBrexitUtil); $this->assertNotEquals('People’s vote!', $result); // Success! } Exiting
  93. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario #4

    The filesystem
  94. @maccath | Katy Ereira | #PHPYorkshire19 Filesystem

  95. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function countHit() {

    $count = file_get_contents(__DIR__ . '/hit_counter.txt'); file_put_contents(__DIR__ . '/hit_counter.txt', ++$count); } Updating a file
  96. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php class HitCounterTest extends

    PHPUnit\Framework\TestCase { public function testCountsHit() { countHit(); } } Updating a file
  97. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $hitCounterFile = __DIR__ . '/../hit_counter.txt'; $countBefore = file_get_contents($hitCounterFile); countHit(); $countAfter = file_get_contents($hitCounterFile); $this->assertEquals($countBefore++, $countAfter); // Success! } Updating a file
  98. @maccath | Katy Ereira | #PHPYorkshire19 Refactoring: Updating a file

    • Inject the filename. • Create a test hit counter file. • Reset the file contents after each test.
  99. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function countHit() {

    $count = file_get_contents(__DIR__ . '/hit_counter.txt'); file_put_contents(__DIR__ . '/hit_counter.txt', ++$count); } Updating a file
  100. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function countHit($file =

    __DIR__ . '/hit_counter.txt') // Inject $file { $count = file_get_contents(__DIR__ . '/hit_counter.txt'); file_put_contents(__DIR__ . '/hit_counter.txt', ++$count); } Updating a file
  101. @maccath | Katy Ereira | #PHPYorkshire19 myLegacyCode.php function countHit($file =

    __DIR__ . '/hit_counter.txt') // Inject $file { $count = file_get_contents($file); // Use $file file_put_contents($file, ++$count); // Use $file } Updating a file
  102. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $hitCounterFile = __DIR__ . '/hit_counter.txt'; $countBefore = file_get_contents($hitCounterFile); countHit(); $countAfter = file_get_contents($hitCounterFile); $this->assertEquals($countBefore++, $countAfter); } Updating a file
  103. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; // Test file! $countBefore = file_get_contents($hitCounterFile); countHit(); $countAfter = file_get_contents($hitCounterFile); $this->assertEquals($countBefore++, $countAfter); } Updating a file
  104. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; $countBefore = file_get_contents($hitCounterFile); countHit($hitCounterFile); // Use test hit counter file. $countAfter = file_get_contents($hitCounterFile); $this->assertEquals($countBefore++, $countAfter); } Updating a file
  105. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function tearDown()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; file_put_contents($hitCounterFile, 0); // Reset counter. } Updating a file
  106. @maccath | Katy Ereira | #PHPYorkshire19 “ vfsStream is a

    stream wrapper for a virtual file system that may be helpful in unit tests to mock the real file system. It can be used with any unit test framework, like PHPUnit or SimpleTest. Fake filesystem Reference: http://vfs.bovigo.org/
  107. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; $countBefore = file_get_contents($hitCounterFile); countHit($hitCounterFile); $countAfter = file_get_contents($hitCounterFile); $this->assertEquals($countBefore++, $countAfter); } Fake filesystem
  108. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function testCountsHit()

    { $vfs = vfsStream::setup(); $hitCounterFile = vfsStream::newFile('test_hit_counter.txt') ->at($vfs) ->setContent('0'); countHit($hitCounterFile->url()); $this->assertEquals(1, $hitCounterFile->getContent()); } Fake filesystem
  109. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function tearDown()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; file_put_contents($hitCounterFile, 0); // Reset counter. } Fake filesystem
  110. @maccath | Katy Ereira | #PHPYorkshire19 tests\HitCounterTest.php public function tearDown()

    { $hitCounterFile = __DIR__ . '/test_hit_counter.txt'; file_put_contents($hitCounterFile, 0); // Reset counter. } Fake filesystem
  111. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario #5

    Spaghetti code
  112. @maccath | Katy Ereira | #PHPYorkshire19 Spaghetti code

  113. @maccath | Katy Ereira | #PHPYorkshire19 Spaghetti code src\Bolognese.php class

    Bolognese { private $eaten; private $parmesan; public function __construct(bool $eaten = false) { … } public function eat() { … } public function isEaten(): bool { … } }
  114. @maccath | Katy Ereira | #PHPYorkshire19 Spaghetti code src\Bolognese.php public

    function eat() { if ($this->eaten) return; // Can’t eat twice! if (!$this->parmesan || !$this->parmesan->isEaten()) { $this->parmesan = new Parmesan(); // Must always have parmesan. } (new GarlicBread())->eat(); // Gotta have garlic bread. $this->parmesan->eat(); $this->eaten = true; }
  115. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php class BologneseTest extends

    PHPUnit\Framework\TestCase { public function testEat() { $bolognese = new Bolognese(); $bolognese->eat(); } } Spaghetti code
  116. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php public function testEat()

    { $bolognese = new Bolognese(); $bolognese->eat(); $this->assertTrue($bolognese->isEaten()); } Spaghetti code
  117. @maccath | Katy Ereira | #PHPYorkshire19 Testing: Spaghetti Code •

    Use @covers annotation to isolate unit under test • Create reusable expectations: ◦ to illustrate different scenarios ◦ to define alternate process branches
  118. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php /** * @covers

    Bolognese */ public function testEat() { $bolognese = new Bolognese(); $bolognese->eat(); $this->assertTrue($bolognese->isEaten()); } Testing: Spaghetti Code
  119. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php public function testEatDevouredBolognese()

    { … } public function testEatUneatenBolognese() { … } Testing: Spaghetti Code
  120. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php private function eatenBolognese()

    { return new Bolognese($eaten = true); } private function uneatenBolognese() { return new Bolognese($eaten = false); } Testing: Spaghetti Code
  121. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php private function expectGarlicBreadToBeEaten()

    { $garlicBread = Mockery::mock('overload:GarlicBread'); return $garlicBread->shouldReceive('eat'); // Return expectation. } Testing: Spaghetti Code
  122. @maccath | Katy Ereira | #PHPYorkshire19 tests\BologneseTest.php public function testEatDevouredBolognese()

    { $this->expectGarlicBreadToBeEaten()->never(); $this->eatenBolognese()->eat(); } public function testEatUneatenBolognese() { $this->expectGarlicBreadToBeEaten()->once(); $this->uneatenBolognese()->eat(); } Testing: Spaghetti Code
  123. @maccath | Katy Ereira | #PHPYorkshire19 Tricky Test Scenario Group

    #6 Private methods
  124. @maccath | Katy Ereira | #PHPYorkshire19 Private methods

  125. @maccath | Katy Ereira | #PHPYorkshire19 Private methods MCHammer.php class

    MCHammer { public function stop() { return $this->cantTouchThis(); } private function cantTouchThis() { return 'hammertime'; } }
  126. @maccath | Katy Ereira | #PHPYorkshire19 Private methods tests\MCHammerTest.php class

    MCHammerTest extends PHPUnit\Framework\TestCase { public function testCantTouchThis() { $mcHammer = new MCHammer(); $result = $mcHammer->cantTouchThis(); // Error; private method! } }
  127. @maccath | Katy Ereira | #PHPYorkshire19 Private methods • Don’t

    test private methods. • Test the public methods that use private methods. • Private methods represent implementation details. • Private methods should remain invisible.
  128. @maccath | Katy Ereira | #PHPYorkshire19 Private methods tests\MCHammerTest.php class

    MCHammerTest extends PHPUnit\Framework\TestCase { public function testCantTouchThis() { $mcHammer = new MCHammer(); $result = $mcHammer->stop(); // Public method! } }
  129. @maccath | Katy Ereira | #PHPYorkshire19 Private methods tests\MCHammerTest.php class

    MCHammerTest extends PHPUnit\Framework\TestCase { public function testCantTouchThis() { $mcHammer = new MCHammer(); $result = $mcHammer->stop(); $this->assertEquals('hammertime', $result); // Success! } }
  130. @maccath | Katy Ereira | #PHPYorkshire19 ?

  131. @maccath | Katy Ereira | #PHPYorkshire19 Thank you! Feedback welcome:

    https://joind.in/talk/87326