Unit Testing and sleep well

Why do we need write unit test? What is a unit test? What is a test double? Why kind of test doubles exist? A light and first look to unit testing.

Transcript

1. Unit Testing and sleep well Jorge Juan Barroso Carmona jorge@karumi.com @flipper83 +JorgeJBarroso Android Expert Android GDE
2. Basho. Poet Karumi is the beauty of ordinary things spoken of in a simple way.
3. Adam Tornhill “Testing is the process of executing a program with the intent of finding errors. ... This definition of testing has many implications ... it implies that testing is a destructive process, even a sadistic process, which explains why most people find it difficult.” Glenford J. Myers
4. Why Write Test?
5. It is your responsibility
6. The only way to makes a refactor
7. it’s really good live Documentation
8. it’s a tool for Design
9. it’s Money
10. “Bad code affect to your Costumer” Martin Fowler
13. Unit Testing
14. 24 different definitions of unit test.
15. Small scope
16. @Test
 public void shouldReturnAValidSumWhenReceivedTwoValidArguments() throws Exception{
 Addition adition = new Addition();
 int add = adition.add(2, 2);
 assertEquals(4, add);
 }
17. A unit is not a class
18. public class MultiplyTest {
 @Test
 public void shouldReturnValidResultWhenMultiplyTwoValues(){ 
 Multiply multiply = new Multiply(new Addition());
 int multiplyValue = multiply.multiply(2, 3);
 assertEquals(6, multiplyValue); 
 }
 }
19. You're testing should be isolated from its collaborators
20. public Calculator(OutputWriter outputWriter, InputReader inputReader, Memory memory) {
 this.outputWriter = outputWriter;
 this.inputReader = inputReader;
 this.memory = memory;
 this.addition = new Addition();
 this.multiply = new Multiply(addition);
 }
21. Unit tests are not silver bullets
22. Fast
 Isolated Repeatable Self-Verifing Timely/Transparent
23. Given
 When Then
24. @Test
 public void shouldShowAdditionResultOnTheOutputStreamWhenCallAdition() throws Exception {
 MockOutputWriter outputWriter = givenOutputWriter();
 InputReader inputReader = givenInputReader(2, 3);
 Memory memory = givenDummyMemory();
 Calculator calculator = givenCalculator(outputWriter, inputReader, memory);
 
 calculator.insertValue();
 calculator.insertValue(); calculator.add();
 
 assertEquals(3, outputWriter.getNumCalls());
 assertEquals(5, outputWriter.getArgumentCatcher());
 }
25. Dummy Stubs Mocks 
 Spies Fake Test Doubles
26. Dummy Not make anything private Memory givenDummyMemory() {
 return new DummyMemory();
 } public class DummyMemory implements Memory {
 @Override
 public void put(int value, int position) {
 }
 
 @Override
 public int get(int memoryPosition) {
 return 0;
 }
 }
27. Stubs Canned responses public class StubInputReader implements InputReader {
 private final int[] values;
 private int count = 0;
 
 public StubInputReader(int... values) {
 this.values = values;
 }
 
 @Override
 public int read() {
 int response = values[count];
 count = (count + 1) % values.length;
 return response;
 }
28. Mocks Expectations public class MockOutputWriter implements OutputWriter {
 private int numCalls;
 private int argument;
 
 @Override
 public void write(int value) {
 numCalls ++;
 argument = value;
 }
 public int getNumCalls() {return numCalls;}
 public int getArgumentCatcher() {return argument;} }

29. Spies Save information public void shouldStoreInMemoryLastOperationResult(){
 … SpyMemory memory = givenSpyMemory(); …
 
 calculator.insertValue();
 calculator.insertValue();
 calculator.add();
 calculator.save(0);
 calculator.insertValue();
 calculator.insertValue();
 calculator.save(1);
 
 List<Integer> values = memory.getValues();
 assertEquals(5, values.get(0).intValue());
 assertEquals(5, values.get(1).intValue());

30. Spies Save information public class SpyMemory implements Memory {
 List<Integer> values = new ArrayList<Integer>();
 @Override
 public void put(int value, int position) {
 values.add(value);
 }
 @Override
 public int get(int memoryPosition) { return 0;}
 
 public List<Integer> getValues() {
 return values;
 }
 }
31. Fake Near to real one shouldShowAdditionResultWhenCallAditionWithSavedValueOnMemory(){
 … Memory memory = givenFakeMemory(); …
 
 calculator.insertValue();
 calculator.insertValue();
 calculator.add();
 calculator.save(0);
 calculator.insertValue();
 calculator.insertValueFromMemory(0);
 calculator.add();
 
 assertEquals(7, outputWriter.getArgumentCatcher());
 }
32. Fake Near to real one public class FakeMemory implements Memory {
 Map<Integer, Integer> mem = new HashMap<Integer, Integer>();
 
 @Override
 public void put(int value, int position) {
 mem.put(position, value);
 }
 
 @Override
 public int get(int memoryPosition) {
 return mem.get(memoryPosition);
 }
 }
33. Adam Tornhill “When you are very thirsty, even dirty water will keep you alive.” J. B. Rainsberger
34. TDD
35. It’s a Design tool
37. Bibliography They’re the cracks! Adicto Al verde. Joaquin Engelmo Elegant?? Unit Testing. Pablo Guardiola Working Effectively with Unit testing. Jay Fields Software Craftmanship. Sandro Mancuso Mocks Aren't Stubs. martin fowler. 2007 Software Reliability: Principles & Practices. Glenford J. Myers 1976 The Art of Unit Testing. Roy Osherove Test Driven Development: By Example. Kent Beck
38. Find me I am very social! jorge@karumi.com @flipper83 +JorgeJBarroso Questions?