Be good to yourself. Write testable code.

Transcript

1. Be good to yourself. Write testable code.
3. SUaaS Suffering as a Service
6. Hi, I’m Adora! Software Engineer, Microsoft Mixed Reality Writer & Youtuber, AdoraHack Twitter: @theadoranwodo
7. Unit tests run against an individual unit of software @theadoranwodo
8. This means we should learn to write code so that we can test each unit of software @theadoranwodo
9. How do we write testable code? @theadoranwodo
10. Question: How do we write testable code? Answer: SOLID Principles @theadoranwodo
11. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle @theadoranwodo
12. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle @theadoranwodo interface Input { Data fetch(); } interface Output { DataObject convertToObject (String result); } interface ProcessManager { String process(Data data); } class ProcessJob { // ... ProcessJob (Input input, Output output, ProcessManager processManager ) { this.input = input; this.output = output; this.processManager = processManager; } DataOutput process() { Data data = this.input.get(); String result = this.processManager .process(data); return this.output.convertToObject(result); } }
13. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle @theadoranwodo
14. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle @theadoranwodo Open to extensions and closed to modifications _______________________________ Practice coding to abstractions, rather than core implementations
15. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle @theadoranwodo
16. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle @theadoranwodo Functions that use references to base classes must be able to use objects of derived classes without knowing it.
17. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle @theadoranwodo
18. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle @theadoranwodo Don’t make clients depend on methods they don’t use
19. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle @theadoranwodo interface Vehicle { void brake(); void truttle(); void clutchDown (); } class MyPrado implements Vehicle{ void brake(){ // code here } void clutchDown (){ /* I don’t need this method but I have to implement it by force so I’d just throw an exception here */ throw new UnsupportedException(); } void truttle(){ // code here } } Don’t do this
20. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle @theadoranwodo interface Vehicle { void brake(); void truttle (); } interface Manual { void clutchDown (); } class MyPrado implements Vehicle { void brake(){ // code here } void truttle (){ // code here } } class MyMaserati implements Vehicle, Manual { void brake(){ // code here } void clutchDown (){ // code here } void truttle (){ // code here } } Do this
21. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle Dependency Inversion Principle @theadoranwodo
22. Question: How do we write testable code? Answer: SOLID Principles Single Responsibility Principle Open/Closed Principle Liskov Substitution Principle Interface Segregation Principle Dependency Inversion Principle @theadoranwodo High level modules should not depend on low level modules, both should depend on abstractions. ________________________________________ Abstractions should not depend on details but details should depend on abstractions
23. @theadoranwodo interface Input { Data fetch(); } interface Output { DataObject convert(String result); } interface ProcessManager { String process(Data data); } class ProcessJob { // ... ProcessJob (Input input, Output output, ProcessManager processManager ) { this.input = input; this.output = output; this.processManager = processManager; } DataOutput process() { Data data = this.input.get(); String result = this.processManager .process(data); return this.output.convert(result); } } ProcessJob Input ProcessManager Output DatabaseInput CustomProcessManager JSONOutput Interface Interface Interface Implementation Implementation Implementation uses uses uses implements implements implements
24. What else can we do to make sure our code is testable? @theadoranwodo
25. @theadoranwodo Dependency Injection. - Loosely coupled code - Ask for what you need, don’t look or try to create. - Each unit should have limited knowledge about other units
26. @theadoranwodo Make sure object creation logic & app logic are different Your application should have two types of classes: - Factories for creating new objects. - Application classes that contain the business logic for your app.
27. @theadoranwodo Respect your constructors Don’t do work in your constructors class Person{ private int buildCode; Person(BuilderHelper helper, int seed){ buildCode = helper.getCodeBuilder () . generateCode (seed) . build(); } } Don’t do this
28. @theadoranwodo Respect your constructors Don’t do work in your constructors class Person{ private int buildCode; Person(int buildCode){ this.buildCode = buildCode; } } Do this instead
29. @theadoranwodo Less static methods Avoid static methods as much as possible: - They are hard to test. - They are hard to mock.
30. Code samples @theadoranwodo
31. Let’s see a common bad real life example @theadoranwodo
32. class Hotel { public Room getRoom(int roomId) { RoomDbClient client = RoomDbClientProvider .getClient(); Room room = null; try { room = client.getRoomRecord(roomId); } catch(DatabaseException ex){ ex.printStackTrace (); } } } class RoomDbClient implements DbClient { // more code above … public Room getRoomRecord(int id) { DbHelper helper = new DbHelper(“room”); //... Room room = helper.read(id); return room; //... } } @theadoranwodo
33. class Hotel { public Room getRoom(int roomId) { RoomDbClient client = RoomDbClientProvider .getClient(); Room room = null; try { room = client.getRoomRecord(roomId); } catch(DatabaseException ex){ ex.printStackTrace (); } } } class RoomDbClient implements DbClient { // more code above … public Room getRoomRecord(int id) { DbHelper helper = new DbHelper(“room”); //... Room room = helper.read(id); return room; //... } } @theadoranwodo
34. class Hotel { public Room getRoom(int roomId) { RoomDbClient client = RoomDbClientProvider .getClient(); Room room = null; try { room = client.getRoomRecord(roomId); } catch(DatabaseException ex){ ex.printStackTrace (); } } } class RoomDbClient implements DbClient { // more code above … public Room getRoomRecord(int id) { DbHelper helper = new DbHelper(“room”); //... Room room = helper.read(id); return room; //... } } @theadoranwodo
35. class Hotel { public Room getRoom(int roomId) { RoomDbClient client = RoomDbClientProvider .getClient(); Room room = null; try { room = client.getRoomRecord(roomId); } catch(DatabaseException ex){ ex.printStackTrace (); } } } class RoomDbClient implements DbClient { // more code above … public Room getRoomRecord(int id) { DbHelper helper = new DbHelper(“room”); //... Room room = helper.read(id); return room; //... } } @theadoranwodo
36. Now, let’s see a basic foobar example @theadoranwodo
37. class Foo { public Bar getBar(int barId) { Rabbit rabbit = new Rabbit(); Animal animal = new Animal(); Bar bar = animal.doSomething (barId, rabbit); return bar; } } @theadoranwodo
38. class Foo { public Bar getBar(int barId) { Rabbit rabbit = new Rabbit(); Animal animal = new Animal(); Bar bar = animal.doSomething (barId, rabbit); return bar; } } @theadoranwodo
39. class Foo { private final Rabbit rabbit; private final Animal animal; public Foo(RabbitFactory rabbitFactory, AnimalFactory animalFactory ){ this.rabbit = rabbitFactory .Create(); this.animal = animalFactory .Create(); } // more code … public Bar getBar(int barId) { Bar bar = animal.doSomething (barId, rabbit ); return bar; } } @theadoranwodo
40. This is Jennifer. Jennifer writes testable code. Her team members love her because it’s easy to understand and test her code. Jennifer is a great Engineer. Be like Jennifer. @theadoranwodo
41. Thank you! www.adoranwodo.com @theadoranwodo