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9 Common Misconceptions about TDD

9 Common Misconceptions about TDD

Exclusive presentation for MageTestFest Florence 2019

HTML Version: https://www.schmengler-se.de/slides/9-common-misconceptions-about-tdd-magetestfest/

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Fabian Schmengler

March 07, 2019
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  1. 9 Common Misconceptions about TDD MAGE TEST FEST

  2. Fabian Schmengler Developer and partner at integer_net Testing Magento since

    2011 @fschmengler
  3. Disclaimer: Beware of straw men Fabian Schmengler /> 9 Common

    misconceptions about TDD @fschmengler
  4. ☼ EINS I have tests, thus I do TDD Fabian

    Schmengler /> 9 Common misconceptions about TDD @fschmengler
  5. TDD Test rst Tests guide development Not TDD Test after

    Test verify development Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  6. ☼ ZWEI Write test, then implement feature Fabian Schmengler />

    9 Common misconceptions about TDD @fschmengler
  7. Red-Green-Refactor In Short Cycles! 1. Write failing test 2. Make

    it pass 3. Make it good Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  8. Red-Green-Refactor In Short Cycles! 1. Write failing test ⬅ one

    little test at at time 2. Make it pass 3. Make it good Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  9. Red-Green-Refactor In Short Cycles! 1. Write failing test ⬅ one

    little test at at time 2. Make it pass ⬅ stupid hacky solution 3. Make it good Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  10. Red-Green-Refactor In Short Cycles! 1. Write failing test ⬅ one

    little test at at time 2. Make it pass ⬅ stupid hacky solution 3. Make it good ⬅ well designed solution Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  11. ☼ DREI No code is ever written without tests Fabian

    Schmengler /> 9 Common misconceptions about TDD @fschmengler
  12. Experiments, "Spikes" Try out the framework Proof of concept Throwaway

    code Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  13. Other ways to experiment Exploratory tests Use failing assertions to

    see real results of unknown operation. e.g.: $this->assertEquals([[], [], []], $result); REPL (Read-Execute-Print-Loop) JS: browser console PHP: n98-magerun2 dev:console Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  14. ☼ VIER When the tests pass, we are done Fabian

    Schmengler /> 9 Common misconceptions about TDD @fschmengler
  15. Iterative vs. Incremental Always refactor Started with a stupid solution

    Design evolves through refactoring Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  16. Changeability & Replacability GeePaw Hill @GeePawHill If I change out

    of my galoshes and in to my tennis shoes, I'm preparing to move faster. Sure, I could run the race in my galoshes. Sure, it will take me a few seconds to take them off. But I'm betting that the cost of changing the shoes will be more than made up during the race. 9 13:32 - 18. Jan. 2019 Weitere T weets von GeePaw Hill ansehen GeePaw Hill @GeePawHill · 18. Jan. 2019 Antwort an @GeePawHill It really is just that simple, not rocket science but basic efficiency: people make this kind of decision every day, where they enhance their performance by doing things that are not themselves performing. Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  17. ☼ FÜNF TDD is a testing technique Fabian Schmengler />

    9 Common misconceptions about TDD @fschmengler
  18. Test Driven A way to write code Tests are means

    to an end (and a welcome side effect) Development ⬆ Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  19. ☼ SECHS No upfront design needed Fabian Schmengler /> 9

    Common misconceptions about TDD @fschmengler
  20. TDD does not replace Requirement analysis Domain Modeling System Design

    API Design => WHAT to build Architects are not becoming unemployed Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  21. ☼ SIEBEN Mock all the collaborators Fabian Schmengler /> 9

    Common misconceptions about TDD @fschmengler
  22. Isolation Isolation From WHAT? External resources: certainly Framework: mostly Except

    for integration tests Libraries: rather not No implementation details. Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  23. Avoid the Mocking Hell Keep Magento dependencies to a minimum

    Mock/stub service contracts (API interfaces), not concrete classes Write adapters for complex or insu cient API Mock or fake those Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  24. ☼ ACHT A unit is a class Fabian Schmengler />

    9 Common misconceptions about TDD @fschmengler
  25. Unit Test Subject Public API of components e.g. Service as

    Facade, and its return types No unit tests for framework integration layer: Controllers Plugins Observers Blocks Resource Models, Repositories Those remain dumb and use our components. Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  26. Unit Test Test behavior, not implementation 1 Test Case !=

    1 Class 1 Test != 1 Method Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  27. Example feature: Subscriptions Orders can be turned into subscriptions Subsequent

    orders are placed automatically Behavior to test A subscription is created if an order has been marked as subscription during checkout Orders are created for active subscriptions with due date Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  28. Subscriptions ├── Cron │ └── HandleSubscriptionsCron.php ⬅ integration layer ├──

    Model │ ├── CreateSubscription.php ⬅ services as public API │ ├── CreateOrders.php │ ├── Subscription.php ⬅ implementation details │ ├── SubscriptionPeriod.php │ ├── SubscriptionStatus.php │ ├── SubscriptionRepository.php ⬅ integration layer, mocked in test │ └── SubscriptionRepositoryInterface.php ├── Plugin │ └── PlaceOrderPlugin.php ⬅ integration layer └── Test ├── Unit │ ├── CreateSubscriptionTest.php ⬅ test behavior │ └── CreateOrdersTest.php └── Integration ├── CronTest.php ⬅ test framework integration ├── PlaceOrderTest.php └── SubscriptionRepositoryTest.php Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  29. Subscriptions ├── Cron │ └── HandleSubscriptionsCron.php ⬅ integration layer ├──

    Model │ ├── CreateSubscription.php ⬅ services as public API │ ├── CreateOrders.php` │ ├── Subscription.php ⬅ implementation details │ ├── SubscriptionPeriod.php │ ├── SubscriptionStatus.php │ ├── SubscriptionRepository.php ⬅ integration layer, mocked in test │ └── SubscriptionRepositoryInterface.php ├── Plugin │ └── PlaceOrderPlugin.php ⬅ integration layer └── Test ├── Unit │ ├── CreateSubscriptionTest.php ⬅ test behavior │ └── CreateOrdersTest.php` └── Integration ├── CronTest.php ⬅ test framework integration ├── PlaceOrderTest.php └── SubscriptionRepositoryTest.php Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  30. Subscriptions ├── Cron │ └── HandleSubscriptionsCron.php ⬅ integration layer ├──

    Model │ ├── CreateSubscription.php ⬅ services as public API │ ├── CreateOrders.php │ ├── Subscription.php ⬅ implementation details │ ├── SubscriptionPeriod.php │ ├── SubscriptionStatus.php │ ├── SubscriptionRepository.php ⬅ integration layer, mocked in test │ └── SubscriptionRepositoryInterface.php ├── Plugin │ └── PlaceOrderPlugin.php ⬅ integration layer └── Test ├── Unit │ ├── CreateSubscriptionTest.php ⬅ test behavior │ └── CreateOrdersTest.php └── Integration ├── CronTest.php ⬅ test framework integration ├── PlaceOrderTest.php └── SubscriptionRepositoryTest.php Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  31. Subscriptions ├── Cron │ └── HandleSubscriptionsCron.php ⬅ integration layer ├──

    Model │ ├── CreateSubscription.php ⬅ services as public API │ ├── CreateOrders.php │ ├── Subscription.php ⬅ implementation details │ ├── SubscriptionPeriod.php │ ├── SubscriptionStatus.php │ ├── SubscriptionRepository.php ⬅ integration layer, mocked in test │ └── SubscriptionRepositoryInterface.php ├── Plugin │ └── PlaceOrderPlugin.php ⬅ integration layer └── Test ├── Unit │ ├── CreateSubscriptionTest.php ⬅ test behavior │ └── CreateOrdersTest.php └── Integration ├── CronTest.php ⬅ test framework integration ├── PlaceOrderTest.php └── SubscriptionRepositoryTest.php Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  32. Exception Testing implementation details can aid development and small scale

    refactoring. BUT those tests can be thrown away when their job is done! Otherwise they stay only as maintenance burden. Let them go! Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  33. ☼ NEUN BDD is better than TDD Fabian Schmengler />

    9 Common misconceptions about TDD @fschmengler
  34. TDD Helps with code design Focus on developers BDD/ATDD Helps

    with requirement analysis Focus on users Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  35. Test Behavior Ideas are not contradictional! With TDD we should

    test behavior as well And why not both? Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  36. Tests in Natural Language Who is really writing their tests

    together with the customer? Expressive test code is possible without Gherkin Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  37. Gherkin Scenario 1: Refunded items should be returned to stock

    Given that a customer previously bought a black sweater from me And I have three black sweaters in stock. When they return the black sweater for a refund Then I should have four black sweaters in stock. PHPUnit public function test_refunded_items_should_be_returned_to_stock() { $this->given_that_a_customer_previously_bought_a_black_sweater_from_me(); $this->and_I_have_three_black_sweaters_in_stock(); $this->when_they_return_the_black_sweater_for_a_refund(); $this->then_I_should_have_four_black_sweaters_in_stock(); } Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  38. ☼ AUS Fabian Schmengler /> 9 Common misconceptions about TDD

    @fschmengler
  39. Coming soon when it's done: Test Driven Magento by Example

    https://tddwizard.com/ @fschmengler Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler
  40. Image sources Rammstein concert: Matt Foster CC-BY 2.0 (colors modi

    ed) Cliparts: pixaby.com (Pixaby Licence, free for commercial usage) Fabian Schmengler /> 9 Common misconceptions about TDD @fschmengler