Chapter 3 Team Exercise

Why do testers automate tests? What are the limitations of automation?

Because it reduces the cost of testing and human error, also it makes regression testing easier because it allows a test to be run repeatedly. Excise tasks are candidates for automation.

Although this is an essential process, it has limitations:

  • Continuous adjustment to testing code
  • Cannot be used for testing UX
  • Script reliability depends on programmer
  • Requires silo elimination

How the inheritance hierarchy can affect controllability and observability?

Having a deep inheritance tree of classes could become more complex to test, because the sub classes are dependent of its father, that means, if we modify or update something in the super class, it will affect all its respective children, which means that every test affected by the modification have to be updated for the sub classes. Therefore, inheritance does not guarantee that a method tested in the context of the super class will work correctly or in the same way that in the context of the sub class or sub classes. Thus, this affects controllability because we will need to control every super class and its sub classes, and if wee have a deep inheritance tree, it will be very complicated. On the other hand, it affects observability becase we need to observe a large number of sub classes that actually are doing the same work as the super class.

Develop JUnit tests for the BoundedQueue class.

You can find the code here.

Delete the explicit throw of NullPointerException in the Min program. Verify that the JUnit test for a list with a single null element now fails.

If we delete the line

if (result == null) throw new NullPointerException ("Min.min");

We can see that the test testForSoloNullElement() fails.

6. Consider the following example class. PrimeNumbers has three methods…

(a) A test that does not reach the fault

void testComputePrimesA() {
PrimeNumbers primeNumbers = new PrimeNumbers();

assertEquals("[]", primeNumbers.toString());
// it never enters the while loop

(b) A test that reaches the fault, but does not infect

void testComputePrimesB() {
PrimeNumbers primeNumbers = new PrimeNumbers();

  assertEquals("[2, 3, 5, 7, 11, 13, 17]",

(c) A test that infects the state, but does not propagate

void testComputePrimesC() {
PrimeNumbers primeNumbers = new PrimeNumbers();

assertEquals("[2, 3, 5, 7, 11, 13, 17, 19]",
// it is affected because it doesn't include 19

(d) A test that propagates, but does not reveal

This test is not possible because the faults starts at the 19 (we’re not taking in consideration 9, because it is not prime), all of subsequent primes that ends in ‘9’ won’t be in the result value.

(e) A test that reveals the fault

void testComputePrimesE() {
PrimeNumbers primeNumbers = new PrimeNumbers();

  assertEquals("[2, 3, 5, 7, 11, 13, 17, 19]",

Exercise 7.

The computePrimes is now using the Sieve of Eratosthenes to find the primes. The first false positive result is again 9, it doesn’t print it, to reach the fault it has to compute the first 7 prime numbers. The RIPR model should be used to know if there’s a fault in our system, on the contrary, we could think that our program is running correctly, but we have so many false positives waiting to be propagated.


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