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!

Transcript

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