TDD

An introduction to the situation of TDD at our company

Transcript

1. TDD Test Driven Development
3. test is written before the corresponding code is written
5. we try to assume nothing about our code, let the tests drive our design
7. tests run all the time, short feedback loop is important
9. be careful for “happy path programming”
10. red green refactor
13. unit tests • test one unit in isolation (SUT) • smallest unit in OOP is the class • use test doubles (mocks, stubs, spies, …) to replace dependencies note: • interfaces can’t be unit tested • abstract classes are difficult to test
15. integration tests • let multiple classes talk to each other in a controlled environment • test side effects in filesystem, database, http calls, … note: These tests will be much slower than unit tests!
17. advantages • confidence that you can change things without breaking something • test suite is a living behavior specification of the code • test suite is a living example of the usage of the code • the red-green-refactor flow tends to take you into the zone
18. example
19. example shopping cart: • add products • remove products • checkout: returns price • after checking out, nothing can be added/ removed
20. class ShoppingCartTest extends PHPUnit_Framework_TestCase { public function test_it_has_a_price_of_zero_without_products() { $cart = new ShoppingCart(); $price = $cart->checkout(); $this->assertEquals(0, $price); } }
21. red
22. final class ShoppingCart { }
23. red
24. final class ShoppingCart { public function checkout() { } }
25. green
26. why green?
27. class ShoppingCartTest extends PHPUnit_Framework_TestCase { // ... public function test_its_price_equals_the_price_of_a_contained_product() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $price = $cart->checkout(); $this->assertEquals(2.20, $price); } }
28. red
29. final class Product { private $name; private $price; public function __construct($name, $price) { $this->name = (string) $name; $this->price = (float) $price; } }
30. red
31. final class ShoppingCart { public function checkout() { } public function add() { } }
32. red
33. final class ShoppingCart { private $total = 0; public function checkout() { return $this->total; } public function add(Product $product) { $this->total = $product->getPrice(); } }
34. red
35. final class Product { private $name; private $price; public function __construct($name, $price) { $this->name = (string) $name; $this->price = (float) $price; } public function getPrice() { return $this->price; } }
36. green
37. public function test_its_price_equals_the_sum_of_prices_of_all_contained_products() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $cheese = new Product('Cheese', 4.50); $cart->add($cheese); $butter = new Product('Butter', 1.00); $cart->add($butter); $price = $cart->checkout(); $this->assertEquals(7.70, $price); }
38. red
39. final class ShoppingCart { private $total = 0; public function checkout() { return $this->total; } public function add(Product $product) { $this->total += $product->getPrice(); } }
40. green
41. refactor
42. tests can be cleaned up: sum of all contained products test also does the sum of one contained product
43. green
44. public function test_it_does_not_count_removed_products_in_the_total_price() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $butter = new Product('Butter', 1.00); $cart->add($butter); $cart->remove($bread); $price = $cart->checkout(); $this->assertEquals(1, $price); }
45. red
46. final class ShoppingCart { // ... public function remove(Product $product) { $this->total -= $product->getPrice(); } }
47. green
48. problem: we can remove items that aren’t in the cart
49. /** * @expectedException CanNotRemoveProduct */ public function test_it_throws_when_trying_to_remove_product_that_it_does_not_have() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $butter = new Product('Butter', 1.00); $cart->remove($butter); }
50. red
51. problem: our current implementation doesn’t know what’s in the cart, only prices. remove the last test to go back to green
52. green
53. refactor
54. final class ShoppingCart { private $products = []; public function checkout() { return array_reduce( $this->products, function($carry, Product $product) { return $carry + $product->getPrice(); } ); } // ...
55. // ... public function add(Product $product) { $this->products[] = $product; } public function remove(Product $product) { array_splice( $this->products, array_search($product, $this->products), 1 ); } }
56. green
57. /** * @expectedException CanNotRemoveProduct */ public function test_it_throws_when_trying_to_remove_product_that_it_does_not_have() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $butter = new Product('Butter', 1.00); $cart->remove($butter); }
58. red
59. final class ShoppingCart { // ... public function remove(Product $product) { if (!in_array($product, $this->products)) { throw new CanNotRemoveProduct(); } array_splice( $this->products, array_search($product, $this->products), 1 ); } }
60. red
61. final class CanNotRemoveProduct extends Exception {}
62. green
63. /** * @expectedException AlreadyCheckedOut */ public function test_it_throws_when_trying_to_add_products_after_checkout() { $cart = new ShoppingCart(); $cart->checkout(); $bread = new Product('Bread', 2.20); $cart->add($bread); }
64. red
65. final class ShoppingCart { private $checkedOut = false; // ... public function checkout() { $this->checkedOut = true; // ... } // ... }
66. final class ShoppingCart { // ... public function add(Product $product) { if ($this->checkedOut === true) { throw new AlreadyCheckedOut(); } // ... } // ... }
67. green
68. /** * @expectedException AlreadyCheckedOut */ public function test_it_throws_when_trying_to_remove_products_after_checkout() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $cart->checkout(); $cart->remove($bread); }
69. red
70. final class ShoppingCart { // ... public function remove(Product $product) { if ($this->checkedOut === true) { throw new AlreadyCheckedOut(); } // ... } }
71. green
72. refactor
73. final class ShoppingCart { // ... public function add(Product $product) { $this->assertNotCheckedOutYet(); // ... } public function remove(Product $product) { $this->assertNotCheckedOutYet(); // ... } }
74. final class ShoppingCart { // ... private function assertNotCheckedOutYet() { if ($this->checkedOut === true) { throw new AlreadyCheckedOut(); } } }
75. green
76. /** * @expectedException CanNotRemoveProduct */ public function test_it_throws_when_trying_to_remove_product_that_it_does_not_have() { $cart = new ShoppingCart(); $bread = new Product('Bread', 2.20); $cart->add($bread); $butter = new Product('Butter', 1.00); $cart->remove($butter); }
77. refactor
78. /** * @expectedException CanNotRemoveProduct */ public function test_it_throws_when_trying_to_remove_product_that_it_does_not_have() { $cart = new ShoppingCart(); $this->addBreadTo($cart); $this->removeButterFrom($cart); }
79. green
80. Unit Testing a Controller
81. class AddToCartControllerTest extends PHPUnit_Framework_TestCase { public function test_it_adds_a_product_and_persists_the_cart() {
 $controller = new AddToCartController(); $request = new Request( 'GET', '/addToCart', array('cartId' => 13, 'productId' => 37) ); $response = $controller->handle($request); $expectedResponse = new Response(200, …); $this->assertEquals($expectedResponse, $response); } }
82. final class AddToCartController { public function handle(Request $request) { return new Response(200, …); } }
83. green
84. class AddToCartControllerTest extends PHPUnit_Framework_TestCase { public function test_it_adds_a_product_and_persists_the_cart() {
 $controller = new AddToCartController(); $request = new Request( 'GET', '/addToCart', array('cartId' => 13, 'productId' => 37) ); $response = $controller->handle($request); $expectedResponse = new Response(200, …); $this->assertEquals($expectedResponse, $response); } }
85. final class AddToCartController { public function handle(Request $request) { // Get product by id (from $request) // Get cart by id (from $request) // Add product to cart // Persist cart // Return a Response } }
86. red
87. final class AddToCartController { private $productRepository; private $cartRepository; public function __construct( ProductRepository $productRepository, CartRepository $cartRepository ) { $this->productRepository = $productRepository; $this->cartRepository = $cartRepository; } public function handle(Request $request) { // … } }
88. final class AddToCartController { // … public function handle(Request $request) { $cartId = $request->param('cartId'); $cart = $this->cartRepository->getById($cartId); } }
89. interface CartRepository { /** * Get a cart by its id * * @param int $cartId * * @return Cart */ public function getById($cartId); }
90. class AddToCartControllerTest extends PHPUnit_Framework_TestCase { public function test_it_adds_a_product_and_persists_the_cart() {
 $controller = new AddToCartController(); $request = new Request( 'GET', '/addToCart', array('cartId' => 13, 'productId' => 37) ); $response = $controller->handle($request); $expectedResponse = new Response(200, …); $this->assertEquals($expectedResponse, $response); } }
91. class AddToCartControllerTest extends PHPUnit_Framework_TestCase { public function test_it_adds_a_product_and_persists_the_cart() { // Same for ProductRepository $cart = new Cart(…);
 $cartRepository = $this->getMock('CartRepository'); $cartRepository->method('getById')->willReturn($cart); $controller = new AddToCartController( $productRepository, $cartRepository ); // … } }
92. final class AddToCartController { // … public function handle(Request $request) { // Same for $product $cartId = $request->param('cartId'); $cart = $this->cartRepository->getById($cartId); $cart->add($product); $this->cartRepository->persist($cart); return new Response(200, …); } }
93. red
94. interface CartRepository { /** * Get a cart by its id * * @param int $cartId * * @return Cart */ public function getById($cartId); /** * Persist a cart * * @param Cart $cart */ public function persist(Cart $cart); }
95. class AddToCartControllerTest extends PHPUnit_Framework_TestCase { public function test_it_adds_a_product_and_persists_the_cart() { // … 
 $cartRepository = $this->getMock('CartRepository'); // … $newCart = new Cart(…); $cartRepository ->expects($this->once()) ->method('persist') ->with($this->equalTo($newCart)); $controller = new AddToCartController( $productRepository, $cartRepository ); // … } }
97. our setup
98. our setup ci-tests • mixture of unit tests and integration tests • access to the whole engagor setup • ran by Jenkins tests • mixture of unit tests and integration tests • access to the whole engagor setup • ran manually
100. $ phpunit --color
101. $ phpunit --color PHPUnit 4.7.6 by Sebastian Bergmann and contributors. ..................................................... 63 / 107 ( 58%) ............................................ Time: 20.86 seconds, Memory: 20.00Mb OK (107 tests, 633 assertions)
102. $ phpunit --testsuite=ci --color
103. $ phpunit --testsuite=ci --color PHPUnit 4.7.6 by Sebastian Bergmann and contributors. ....................................................... 65 / 85 ( 76%) .................... Time: 162 ms, Memory: 16.75Mb OK (85 tests, 107 assertions)
104. read also • https://en.wikipedia.org/wiki/Test-driven_development • http://martinfowler.com/bliki/TestDrivenDevelopment.html • http://verraes.net/2015/01/economy-of-tests/ • http://verraes.net/2014/12/how-much-testing-is-too-much/ • https://phpunit.de/manual/current/en/index.html • full code example: https://gist.github.com/anonymous/ bb5cdc52dab655bbd9d6
105. thanks