Effective Unit Testing - Speaker Deck

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有效的單元測試 Jace Ju @ KKBOX https://commons.wikimedia.org/

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一直以來，我們寫的測試就像…

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捫心自問，你寫的測試有用嗎？

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如果你常有這些抱怨… 測試容易因為執行環境問題而失敗同事說看不懂你在測試什麼新增或修改測試要做的事很多常常沒有測試到真正重要的部份

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你就需要瞭解測試的… 測試替身可讀性可維護性可靠性

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測試替身 Test Doubles https://www.pinterest.com

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待測程式碼真實物件測試替身測試替身測試替身

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替身的作用隔離待測程式加速測試執行讓測試結果穩定模擬特殊狀況曝露隱藏的行為

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替身的類型 Stub Fake Spy Mock

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Stub 繼承或實作相依類別與介面寫死的回傳值 (包含 Exception) Extract And Override

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class StubRepository implements RepositoryInterface { public function findUser(int $id): User { return new StubUser([ 'id' => 1 ]); } public function fetchUsers(array $ids): Collection { throw new \InvalidArgumentException(); } } Stub 範例

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Fake 提供輕量級實作執行速度很快建立成本較低

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class FakeSession implements SessionInterface { private $storage = []; public function put($name, $value) { $this->storage[$name] = $value; } public function get($name) { return $this->storage[$name] ?? null; } } Fake 範例

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Laravel 中的應用

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Spy 在相依物件上加入 spy 程式記錄相依物件的方法有無被呼叫事後透過 spy 物件的方法驗證

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$logger = Mockery::spy(Logger::class); $auth = new Auth($logger); $auth->login('user', 'pass'); $logger->shouldHaveReceived('log') ->once(); Spy 範例

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Mock 進階版的 Stub 和 Spy 讓不同輸入參數對應不同輸出精準控制方法的被呼叫次數

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$service = Mockery::mock(UserService::class); $service->shouldReceive('authenticate') ->with('jaceju', '123456') ->andReturn(false); $service->shouldReceive('authenticate') ->with('butany', '123456') ->andReturn(true); $userController = new UserController($service); $actual = $userController->login('jaceju', '123456'); $this->assertFalse($actual); $actual = $userController->login('butany', '123456'); $this->assertTrue($actual); Mock 範例

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Spy - 事後驗證行為 Mock - 事前定義對應輸出

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替身反模式 • 所有相依類別都用替身隔離假測試 • 重構時也必須去修改測試中的替身過度的實作耦合 • 資料庫邏輯被徹底隔離設計過當 https://speakerdeck.com/adamwathan/tdd-the-good-parts-1

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替身反模式解法 • 可控制的部份就別用替身使用真實協作物件 • 從抽象層次去驗證需求別驗證細節 • 測試時改用 sqlite::memory: 使用 ORM

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替身就是造假的藝術 https://zh.wikipedia.org/

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可讀性 Readability http://uxmastery.com/

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可讀性原則別讓閱讀者思考一個測試只測試一個情境

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可讀性反模式斷言不直覺斷言範圍太廣一次測太多事過份保護

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斷言不直覺 $this->assertTrue(array_key_exists('foo', $ary)); $this->assertEquals(3, strpos('foobar', 'bar'));

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用更直覺的斷言 $this->assertArrayHasKey('foo', $ary); $this->assertContains('bar', 'foobar');

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/** @expectedException \Exception */ public function textServiceShouldThrowExceptionWhenSomethingWrong() { // ... $service = new UserService(); $service->getVerifiedUsers(); } 斷言範圍太廣

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/** * @expectedException \Illuminate\Database\QueryException */ public function textThrowExceptionWhenQueryFailed() { // ... $service = new UserService(); $service->getVerifiedUsers(); } /** * @expectedException \Predis\Connection\ConnectionException */ public function textThrowExceptionWhenRedisIsDisconnect() { // ... $service = new UserService(); $service->getVerifiedUsers(); } 縮小斷言範圍

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public function testAlbum() { $albumId = 10001; $albumIds = [$albumId]; $wrapper = new ImageApiWrapper(); $actual = $wrapper->getAlbumUrls($albumIds); $this->assertEquals('10001/300x300.jpg', $actual[$albumId]); $actual = $wrapper->getAlbumInfos($albumIds); $this->assertEquals('10001/300x300.jpg', $actual[$albumId]['url']); } 一次測太多事

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protected function setUp() { $this->wrapper = new ImageApiWrapper(); } public function testGetAlbumUrlsSuccess() { $albumId = 10001; $expected = [ $albumId => '10001/300x300.jpg', ]; $actual = $this->wrapper->getAlbumUrls([$albumId]); $this->assertEquals($expected, $actual); } 一次只測一件事

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public function testGetAlbumInfoSuccess() { $albumId = 10001; $expected = [ $albumId => [ 'id' => '10001', 'url' => '10001/300x300.jpg', ], ]; $actual = $this->wrapper->getAlbumInfos([$albumId], 'tw'); $this->assertEquals($expected, $actual); } 一次只測一件事 (續)

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$users = (new UserRepository())->fetchVerifiedUsers(); $this->assertNotNull($users); $this->assertCount(5, $users); 過度保護

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$users = (new UserRepository())->fetchVerifiedUsers(); $this->assertNotNull($users); $this->assertCount(5, $users); 刪除不必要的斷言

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可維護性 Maintainability http://soniasaelensdeco.canalblog.com/

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可維護性原則不論誰接手都能運作減少不穩定的狀況

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可維護性反模式條件邏輯重複的程式碼相依的測試脆弱的測試

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$service = new UserService(); $verifiedUsers = $service->getVerifiedUsers(); foreach ($verifiedUsers as $index => $verifiedUser) { if ($index === 0) { $this->assertEquals('butany', $verifiedUser['name']); } if ($index === 1) { $this->assertEquals('jaceju', $verifiedUser['name']); } } 條件邏輯

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public function testUserServiceShouldReturnExpectedVerifiedUsers() { $service = new UserService(); $verifiedUsers = $service->getVerifiedUsers(); $this->assertCount(2, $verifiedUsers); $this->assertArrayHasKey('name', $verifiedUsers[0]); $this->assertEquals('butany', $verifiedUsers[0]['name']); $this->assertArrayHasKey('name', $verifiedUsers[1]); $this->assertEquals('jaceju', $verifiedUsers[1]['name']); } 重複的程式碼

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class UserServiceTest { use AssertionHelper; private $service; public function setUp() { $this->service = new UserService(); } } trait AssertionHelper { private function assertArrayHasKeyWithValue($array, $key, $value) { $this->assertArrayHasKey($key, $array); $this->assertEquals($value, $array[$key]); } } 利用 setUp 和 Trait

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public function testUserServiceShouldReturnExpectedVerifiedUsers() { $verifiedUsers = $this->service->getVerifiedUsers(); $this->assertCount(2, $verifiedUsers); $this->assertArrayHasKeyWithValue($verifiedUsers[0], 'name', 'butany'); $this->assertArrayHasKeyWithValue($verifiedUsers[1], 'name', 'jaceju'); } 利用 setUp 和 Trait (續)

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class ConfigTest extends TestCase { private $config; public function testAddConfigSuccess() { $configFile = __DIR__ . '/fixture/config.json'; $this->config = new Config($configFile); $this->config->add('debug', true); $this->assertObjectHasAttribute('debug', $this->config); } public function testInjectConfigToAppShouldWork() { $app = new App($this->config); assertThat($app->debugMode, isTrue()); } } 相依的測試

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class AppTest extends TestCase { public function testInjectConfigToAppShouldWork() { $config = Mockery::mock(Config::class); $config->shouldRecive('toArray') ->andReturn(['debug' => true]); $app = new App($config); assertThat($app->debugMode, isTrue()); } } 獨立每個測試案例

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脆弱的測試不可控的執行環境寫死的檔案路徑緩慢的等待 (Sleep)

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可靠性 Reliability

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可靠性原則去除任何的疑惑要真正是可信賴的

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可靠性反模式被註解的測試永不失敗的測試虛假的測試有條件的測試

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class AppTest extends TestCase { public function testInjectConfigToAppShouldWork() { // $config = Mockery::mock(Config::class); // $config->shouldRecive('toArray') // ->andReturn(['debug' => true]); // $app = new App($config); // assertThat($app->debugMode, isTrue()); } } 被註解的測試

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class ImageApiWrapperTest extends TestCase { public function testDevelopmentMode() { $dev = true; $app = new ImageApiWrapper($dev); } } 永不失敗的測試

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/** @test */ public function it_should_get_empty_array_when_get_urls_with_invalid_id() { $albumId = 'invalid_id'; $albumIds = [$albumId]; $wrapper = new ImageApiWrapper(); $actual = $wrapper->getAlbumUrls($albumIds); $expected = [ $albumId => 'noimg/300x300.jpg', ]; $this->assertEquals($expected, $actual); } 虛假的測試

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public function testRunListCommandAtHomeDirectory() { $expectedFile = 'hello.txt'; $targetDirectory = '/home/jaceju'; $this->createFile($expectedFile, $targetDirectory); $command = new ListCommand($targetDirectory); $process = Process::run($command); if ($process->getExitCode() === 0) { $this->assertEquals($expectedFile, $process->getOutput()); } } 有條件的測試

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public function testRunListCommandAtHomeDirectoryShouldGetExpectedFile() { $expectedFile = 'hello.txt'; $targetDirectory = '/home/jaceju'; $this->createFile($expectedFile, $targetDirectory); $command = new ListCommand($targetDirectory); $process = Process::run($command); $this->assertEquals(0, $process->getExitCode()); $this->assertEquals($expectedFile, $process->getOutput()); } 用斷言取代條件式

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總結 Summary https://www.bankinghub.eu/

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驗證需求而不是驗證細節。一次只測試一件事。要有清楚的斷言。只隔離不可控的因素。