07 - Definição de classes e manipulação de objetos

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Software Testing 
Software 
User 
Software Testing 
Software 
User 
Test 
Case Study: Factoring Integer 
Numbers 
 
Adapted from: http://homepages.dcc.ufmg.br/~fernando/classes/dcc052/ementa/lesson3/ 
Objective 
• Write a class PrimeFactorizer, that, given 
an integer number, returns an array with all 
the prime factors of this number. 
Writing a Unit Test 
package juTestingEx; 
 
import junit.framework.TestCase; 
 
public class TestFactors extends TestCase { 
 
 public TestFactors(String name) { 
 super(name); 
 } 
 
 public void testEx() throws Exception { 
 int tmp = 2 * 2; 
 assertEquals(4, tmp); 
 } 
} 
 
Writing a Unit Test 
What are good tests? 
• Automated and repeatable 
• Easy to implement 
• Once written, remain for future use 
• Run at the push of the button 
• Orthogonal (non-redundant behavior) 
A Simple Test Case 
• What is the simplest test case that our 
Factorizer should pass? 
 
 
A Simple Test Case 
 public void testTwo() { 
 
 int factors[] = PrimeFactorizer.factor(2); 
 
 assertEquals(1, factors.length); 
 assertEquals(2, factors[0]); 
 } 
 
We wrote the test without really having the program to be tested. This is called 
intentional programming. 
A Simple Program 
• What is the smallest program that we can 
create so that our app compiles? 
 
A Simple Program 
package juTestingEx; 
 
public class PrimeFactorizer { 
 
 public static int[] factor(int i) { 
 return null; 
 } 
} 
 
What is the difference between a test error and a test failure? 
A Simple Program 
• What is the minimum program that we can 
write so that our application passes the test?
 
A Simple Program 
package juTestingEx; 
 
public class PrimeFactorizer { 
 
 public static int[] factor(int i) { 
 return new int[] {2}; 
 } 
} 
 
Checkstyle 
• Is a development tool to help programmers write 
Java code that adheres to a coding standard. 
• Automates the process of checking Java code to 
spare humans of this boring (but important) task. 
This makes it ideal for projects that want to 
enforce a coding standard. 
• Supports the Sun Code Conventions 
• Is available at http://checkstyle.sourceforge.net/ 
Checkstyle 
 ArrayTrailingComma 
Description 
Checks that array initialization contains a trailing comma. 
int[] a = new int[] 
{ 
 1, 
 2, 
 3, 
}; 
 
The check allows to not add a comma if both left and right curlys are on the same line. 
return new int[] { 0 }; 
 
Rationale: Putting this comma in makes it easier to change the order of the elements or add 
new elements on the end. 
 
 
A Simple Program “style checked” 
package com.primeFactorizer; 
/** 
 * This class factorizes a prime number. 
 * @author jefersson 
 * 
 */ 
public final class PrimeFactorizer { 
 
 /** 
 * Private constructor to avoid instantiation. 
 */ 
 private PrimeFactorizer() { } 
 
 /** 
 * This method factors an integer number. 
 * @param i the number to be factored out. 
 * @return an array of integers, where each element is a factor of i. 
 */ 
 public static int[] factor(final int i) { 
 return new int[] {2}; 
 } 
} 
A Simple Program “style checked” 
package com.primeFactorizer; 
/** 
 * This class factorizes a prime number. 
 * @author jefersson 
 * 
 */ 
public final class PrimeFactorizer { 
 
 /** 
 * Private constructor to avoid instantiation. 
 */ 
 private PrimeFactorizer() { } 
 
 /** 
 * This method factors an integer number. 
 * @param i the number to be factored out. 
 * @return an array of integers, where each element is a factor of i. 
 */ 
 public static int[] factor(final int i) { 
 return new int[] {2}; 
 } 
} 
Why? 
A Simple Program “style checked” 
package com.primeFactorizer; 
/** 
 * This class factorizes a prime number. 
 * @author jefersson 
 * 
 */ 
public final class PrimeFactorizer { 
 
 /** 
 * Private constructor to avoid instantiation. 
 */ 
 private PrimeFactorizer() { } 
 
 /** 
 * This method factors an integer number. 
 * @param i the number to be factored out. 
 * @return an array of integers, where each element is a factor of i. 
 */ 
 public static int[] factor(final int i) { 
 return new int[] {2}; 
 } 
} 
Why? 
• Thread safety 
• Minor compiler optimizations 
• Documentation 
A Simple Test Case 
• What is the simplest test case we can add to 
this? 
 
 
 
A Simple Test Case 
• What is the simplest test case we can add to 
this? 
 
 
 
public final void testThree() throws Exception { 
 int[] factors = PrimeFactorizer.factor(3); 
 assertEquals(1, factors.length); 
 assertEquals(3, factors[0]); 
} 
 
A Simple Program 
• And what is the simplest way to make our 
program to pass the test? 
 
 
A Simple Program 
• And what is the simplest way to make our 
program to pass the test? 
 
 
 public static int[] factor(final int i) { 
 if (i == 2) { 
 return new int[] { 2 }; 
 } else { 
 return new int[] { 3 }; 
 } 
 } 
 
Refactoring 
• “Is a controlled technique for improving the 
design of an existing code base” 
 (M. Fowler, 1999) 
 
 
 
 
 
Some references: 
http://www.ben-morris.com/why-refactoring-code-is-almost-always-better-than-rewriting-it 
http://refactoring.com/ 
Code Refactoring 
• How could we refactor this code, to make it 
more general? 
 
public static int[] factor(final int i) { 
 
 return new int[] { i }; 
} 
 
Code Refactoring 
• How could we refactor this code, to make it 
more general? 
 
public static int[] factor(final int i) { 
 
 return new int[] { i }; 
} 
 
The name 'i' is not very meaningful. Let's do some more refactoring? 
Code Refactoring 
• How could we refactor this code, to make it 
more general? 
 
public static int[] factor(final int multiple) { 
 
 return new int[] { multiple }; 
} 
 
A New Test 
• What is the next test that we should add? 
 
A New Test 
• What is the next test that we should add? 
 public static int[] factor(int multiple) { 
 // Compute the new factors: 
 int currentFactor = 0; 
 int[] factorRegister = new int[2]; 
 for (; (multiple % 2) == 0; multiple /= 2) { 
 factorRegister[currentFactor++] = 2; 
 } 
 if (multiple != 1) { 
 factorRegister[currentFactor++] = multiple; 
 } 
 // Trim the array, so that we pass the tests: 
 int[] factors = new int[currentFactor]; 
 for (int i = 0; i < currentFactor; i++) { 
 factors[i] = factorRegister[i]; 
 } 
 return factors; 
 } 
More Refactoring... 
• The code is messy. What are the problems? 
 public static int[] factor(int multiple) { 
 // Compute the new factors: 
 int currentFactor = 0; 
 int[] factorRegister = new int[2]; 
 for (; (multiple % 2) == 0; multiple /= 2) { 
 factorRegister[currentFactor++] = 2; 
 } 
 if (multiple != 1) { 
 factorRegister[currentFactor++] = multiple; 
 } 
 // Trim the array, so that we pass the tests: 
 int[] factors = new int[currentFactor]; 
 for (int i = 0; i < currentFactor; i++) { 
 factors[i] = factorRegister[i]; 
 } 
 return factors; 
 } 
More Refactoring... 
• The code is messy. What are the problems? 
 publicstatic int[] factor(int multiple) { 
 // Compute the new factors: 
 int currentFactor = 0; 
 int[] factorRegister = new int[2]; 
 for (; (multiple % 2) == 0; multiple /= 2) { 
 factorRegister[currentFactor++] = 2; 
 } 
 if (multiple != 1) { 
 factorRegister[currentFactor++] = multiple; 
 } 
 // Trim the array, so that we pass the tests: 
 int[] factors = new int[currentFactor]; 
 for (int i = 0; i < currentFactor; i++) { 
 factors[i] = factorRegister[i]; 
 } 
 return factors; 
 } 
Many concepts in the same function! 
1. package com.primeFactorizer; 
2. 
3. import java.util.Vector; 
 
4. public final class PrimeFactorizer { 
5. private static int factorIndex; 
6. private static int[] factorRegister; 
7. private PrimeFactorizer() { } 
8. public static int[] factor(int multiple) { 
9. initialize(); 
10. findPrimeFactors(multiple); 
11. return copyToResult(); 
12. } 
13. private static void initialize() { 
14. factorIndex = 0; 
15. factorRegister = new int[2]; 
16. } 
17. private static void findPrimeFactors(final int multiple) { 
18. int aux = multiple; 
19. for (; (aux % 2) == 0; aux /= 2) { 
20. factorRegister[factorIndex++] = 2; 
21. } 
22. if (aux != 1) { 
23. factorRegister[factorIndex++] = aux; 
24. } 
25. } 
26. private static int[] copyToResult() { 
27. int[] factors = new int[factorIndex]; 
28. for (int i = 0; i < factorIndex; i++) { 
29. factors[i] = factorRegister[i]; 
30. } 
31. return factors; 
32. } 
33. } 
 
A New Test 
• What is the next test that we should add? 
 
A New Test 
• What is the next test that we should add? 
 public final void testFour() throws Exception { 
 int[] factors = PrimeFactorizer.factor(4); 
 assertEquals(2, factors.length); 
 assertEquals(2, factors[0]); 
 assertEquals(2, factors[1]); 
 
} 
 
public final void testFive() throws Exception { 
 int[] factors = PrimeFactorizer.factor(5); 
 assertEquals(1, factors.length); 
 assertEquals(5, factors[0]); 
} 
 
A New Test 
• What is the next test that we should add? 
 public final void testFour() throws Exception { 
 int[] factors = PrimeFactorizer.factor(4); 
 assertEquals(2, factors.length); 
 assertEquals(2, factors[0]); 
 assertEquals(2, factors[1]); 
 
} 
 
public final void testFive() throws Exception { 
 int[] factors = PrimeFactorizer.factor(5); 
 assertEquals(1, factors.length); 
 assertEquals(5, factors[0]); 
} 
 Do we have to change the code to pass 4 and 5? 
1. package com.primeFactorizer; 
2. 
3. import java.util.Vector; 
 
4. public final class PrimeFactorizer { 
5. private static int factorIndex; 
6. private static int[] factorRegister; 
7. private PrimeFactorizer() { } 
8. public static int[] factor(int multiple) { 
9. initialize(); 
10. findPrimeFactors(multiple); 
11. return copyToResult(); 
12. } 
13. private static void initialize() { 
14. factorIndex = 0; 
15. factorRegister = new int[2]; 
16. } 
17. private static void findPrimeFactors(final int multiple) { 
18. int aux = multiple; 
19. for (; (aux % 2) == 0; aux /= 2) { 
20. factorRegister[factorIndex++] = 2; 
21. } 
22. if (aux != 1) { 
23. factorRegister[factorIndex++] = aux; 
24. } 
25. } 
26. private static int[] copyToResult() { 
27. int[] factors = new int[factorIndex]; 
28. for (int i = 0; i < factorIndex; i++) { 
29. factors[i] = factorRegister[i]; 
30. } 
31. return factors; 
32. } 
33. } 
 
What is the next test case that will fail? 
A New Test 
• How to make it pass testEight? 
public final void testEight() throws Exception { 
 int[] factors = PrimeFactorizer.factor(8); 
 assertEquals(3, factors.length); 
 assertEquals(2, factors[0]); 
 assertEquals(2, factors[1]); 
 assertEquals(2, factors[2]); 
 } 
 
1. We must increase the size of the array of factors, but, which size to use? 
A New Test 
• How to make it pass testEight? 
public final void testEight() throws Exception { 
 int[] factors = PrimeFactorizer.factor(8); 
 assertEquals(3, factors.length); 
 assertEquals(2, factors[0]); 
 assertEquals(2, factors[1]); 
 assertEquals(2, factors[2]); 
 } 
 
1. We must increase the size of the array of factors, but, which size to use? 
2. What is the largest number of factors an integer can have? 
A New Test 
• How to make it pass testEight? 
public final void testEight() throws Exception { 
 int[] factors = PrimeFactorizer.factor(8); 
 assertEquals(3, factors.length); 
 assertEquals(2, factors[0]); 
 assertEquals(2, factors[1]); 
 assertEquals(2, factors[2]); 
 } 
 
1. We must increase the size of the array of factors, but, which size to use? 
2. What is the largest number of factors an integer can have? 
3. What is the largest integer that we can handle? 
A New Test 
• How to make it pass testEight? 
public static final int MAX_NUM_FACTORS = 64; 
 
private static void initialize() { 
 factorIndex = 0; 
 factorRegister = new int[MAX_NUM_FACTORS]; 
} 
 
1. package com.primeFactorizer; 
2. 
3. import java.util.Vector; 
 
4. public final class PrimeFactorizer { 
5. private static int factorIndex; 
6. private static int[] factorRegister; 
7. public static final int MAX_NUM_FACTORS = 64; 
8. private PrimeFactorizer() { } 
9. public static int[] factor(int multiple) { 
10. initialize(); 
11. findPrimeFactors(multiple); 
12. return copyToResult(); 
13. } 
14. private static void initialize() { 
15. factorIndex = 0; 
16. factorRegister = new int[MAX_NUM_FACTORS]; 
17. } 
18. private static void findPrimeFactors(final int multiple) { 
19. int aux = multiple; 
20. for (; (aux % 2) == 0; aux /= 2) { 
21. factorRegister[factorIndex++] = 2; 
22. } 
23. if (aux != 1) { 
24. factorRegister[factorIndex++] = aux; 
25. } 
26. } 
27. private static int[] copyToResult() { 
28. int[] factors = new int[factorIndex]; 
29. for (int i = 0; i < factorIndex; i++) { 
30. factors[i] = factorRegister[i]; 
31. } 
32. return factors; 
33. } 
34. } 
 
What is the next test case that will fail? 
A New Test 
• How to make it pass testNine? 
public final void testNine() throws Exception { 
 int[] factors = PrimeFactorizer.factor(9); 
 assertEquals(2, factors.length); 
 assertEquals(3, factors[0]); 
 assertEquals(3, factors[1]); 
} 
 
• How this would extends to 25? 
A New Test 
• How to make it pass testNine? 
public final void testNine() throws Exception { 
 int[] factors = PrimeFactorizer.factor(9); 
 assertEquals(2, factors.length); 
 assertEquals(3, factors[0]); 
 assertEquals(3, factors[1]); 
} 
 
• How this would extends to 25? 
Refactoring... 
• Can you see the loop pattern? 
private static void findPrimeFactors(final int multiple){ 
 int aux = multiple; 
 for (int factor = 2; aux != 1; factor++) { 
 for (; (aux % factor) == 0; aux /= factor) { 
 factorRegister[factorIndex++] = factor; 
 } 
 } 
} 
 
 
Javadoc 
 
Adapted from: http://homepages.dcc.ufmg.br/~fernando/classes/dcc052/ementa/lesson3/ 
Comments 
Comments 
/** 
 * This class factorizes a prime number. 
 * @author jefersson 
 * 
 */ 
public final class PrimeFactorizer { 
 
 // ERROAQUI! 
 for (int factor = 2; aux != 1; factor++) { 
 for (; (aux % factor) == 0; aux /= factor) { 
 factorRegister[factorIndex++] = factor; 
 } 
 } 
How to Write Doc Comments for the Javadoc Tool: 
http://www.oracle.com/technetwork/java/javase/documentation/index-137868.html