Test Assignment 2

1. Reflections

1.1 Computer Mouse

Identify the types of testing you would perform on a computer mouse, to make sure that it is of the highest quality.

Unit tests

• Laser sensor works and generates some sort of output
• Right and left mousebutton generates output when pressed, and no output when not pressed
• Scrollwheel generates one output when scrolled one way, and another output when scrolled the other way

Integration tests

• The controller-unit receives the expected input from the laser sensor in the expected format
• The controller-unit can differentiate between the right and left mousebuttons being pressed and not pressed
• The controller-unit can differentiate between the scrollwheel being scrolled one way, and being scrolled the other way

System tests

• The inputs and outputs of the mouse are tested as a complete system

Acceptance tests

• The mouse fulfills the clients requirements
• The mouse acts and reacts as the client has previously described

1.2 Catastrophic Failure

Find a story where a software system defect had a bad outcome. Describe what happened. Can you identify a test that would have prevented it?

The Therac-25 case:
The Therac-25 was a radiation therapy machine produced in the early 1980s. It was used in the treatment of cancer patients, delivering controlled doses of radiation to target and destroy cells. The machine could operate in two modes: a direct electron beam, and a more powerful X-ray mode.

The defect:
If an operator entered a particular sequence of keystrokes with a certain timing, the software could mistakenly set up the machine in a high-power mode without the necessary metal target in place.

Prevention:
To prevent this defect, the developers could have implemented an integration test, which ensures that the high-power mode is only accessible when the necessary metal target is confirmed to be in place.

3. Investigation of tools

3.1 JUnit 5

Investigate JUnit 5 (Jupiter). Explain the following, and how they are useful:

@Tag
Tags can be put on tests, which can then later be used to filter tests at runtime. You can for example choose to only run tests tagged with "CustomerTests"

@Disabled
These tests will not be executed

@RepeatedTest
These tests will be run a specified number of times

@BeforeEach, @AfterEach
Methods with these annotations will be run either before or after each test

@BeforeAll, @AfterAll
Methods with these annotations will be run once either before or after all the tests

@DisplayName
This annotation is used to provide tests with a more easily readable name. Can make results more descriptive

@Nested
Can be used to nest tests within eachother. Useful if related tests needs to be grouped

assumeFalse, assumeTrue
Can be used to abandon a test, without marking it as failed, if a certain condition is not met at the start of the test

3.2 Mocking Frameworks

Investigate mocking frameworks for your preferred language. Choose at least two frameworks, and answer the questions:

Mockito and JMockit

What are their similarities?\

• They have the same purpose. Used to create mock objects in unit tests
• Both frameworks utilize annotations
• Both allow for setting expectations on mock objects
• Both allow for veryfing whether or not certain methods were called on mock objects
• Both allow to set up mock methods

What are their differences?\

• Quite different syntax
• Until version 2, Mockito didnt support mocking of final methods and classes
• In Mockito, you'd need additional tools to mock constructors and static methods
• JMockit natively supports mocking only certain methods of an instance. Mockito requires the use of spy()

Which one would you prefer, if any, and why?
I would prefer Mockito. Mockito is more popular in the Java community, which results in more documentation, and better support. Mockito's API is also known to be simpler, which is better suited for newcomers.