Worksheet: J1

Worksheets are self-guided activities that reinforce lectures. They are not graded for accuracy, only for completion. Worksheets are due by Sunday night before the next lecture.

Create a new repo using all the steps in Lab 0 called yourgitusername-worksheet-J1.

Please submit your answers to the questions as comments in the java file you’ll be writing in this lab, which you should add to your repo.

Questions

1. What is fault localization?

   Reveal Solution

   Fault localization typically involves tracing back from the line of code producing the incorrect output to where the problem actually was. To do this, a failing test case is needed, as well as the ability to trace through code, whether with print statements or a debugger.

2. What are three benefits of Test Driven Development (TDD)?

   Reveal Solution

   • Your tests are not biased by your code
   • Writing tests helps you think about how you might write code
   • Writing tests helps you think about the requirements of your system

3. Given the example of requirements for generating a password:

   • It must have at least one number.
   • It must have at least one uppercase letter.
   • It must have at least one lowercase letter.
   • It must not contain the website gmail anywhere. (For example if we were generating a password for gmail accounts)
   • It can only be made up of letters, numbers, and the underscore.

   What are the input domain paritions for this exercise?

   Reveal Solution

   First, we have valid and invalid passwords:

   • invalid
   • valid

   But each of these groups can be refined as:

   • invalid
   • • missing uppercase letter
   • • missing lowercase letter
   • • missing number
   • • missing all combinations of the three items above
   • • contains gmail
   • • contains non-valid characters
   • valid

   Although the question did not ask for this, more tests could/should be generated by looking at the edge cases between these partitions.

4. Complete the truth table below to show what inputs we need to achieve active clause coverage for the following conditional:

   if ( ( (a > b) or G ) and (x < y) )
   

   a > b

   G

   x < y

   predicate outcome

   clause responsible

   Reveal Solution

   a > b	G	x < y	predicate outcome	clause responsible
   T	T	T	T	x < y
   T	T	F	F	x < y
   F	T	T	T	G
   F	F	T	F	G
   T	F	T	T	a > b
   F	F	T	F	a > b

5. Consider the control flow graph below. What are all the paths (using node numbers) that would achieve full path coverage as a test criteria? Is this a finite set?

   

   Reveal Solution

   The set is infinite because of the loop between 3 and 4:

   `
   12567
   1257
   13567
   1357
   1343567
   134357
   13434567
   1343457
   134..567
   134..67
   `

6. What benefit does mutation testing offer over other testing methods discussed in class?

   Reveal Solution

   Mutation testing is automated, in the sense that it solves the oracle problem: there is no need to define expected outputs, because we assume the current functionality of the program under test is correct (and therefore the correct output). Our goal is not to test the correctness of this code directly, but to test how complete/effective our test suite is. The assumption is that real bugs will be found in the code if we generate a robust enough test suite.

7. Convert your DriverJava1_sample.java file from the previous lecture into a Junit test file with the following elements:

   • a single unit test for every input class (give it the name of that input partition) – if you have more than 20 tests, you can skip the rest.

   Assume that the method under test is called checkCode that takes a string as an argument and returns a boolean value whether or not the input was a valid code.

   This is how we will also record that you attempted the in-class example from lecture. Your code doesn’t need to compile.

   Reveal Solution

   Answers will vary, but here is a template for your tests:

   
   import org.junit.Test;
   import static org.junit.Assert.*;
   import java.io.*;
   
   public class CheckCodeTester {
   
       @Test
       public void valid_inputs() {
           assertEquals(true, checkCode("Hi9_jf5D3r"));
       }   
   
       // your other tests here
   }