1. Chapter 4 Software Testing and Tools
Software Development
Chapter 4
Software Testing and Tools

2. Testing
Software testing involves a series of processes to verify that :
The finished product meets the original specification
The software is robust
The software is reliable
Testing can only find errors in a program, not prove there are none
Testing should be systematic
Test data needs to be planned and the test process needs to record a test log
The actual test data selected depends on the test strategy used

3. Test Strategies Recapping testing methods..
Module Testing, on all components
Integration Testing, where the components function as an entity
System Testing or Black Box Testing
Acceptance Testing or Beta Testing, ensuring that the system is ready for operational use
Software testing is a complex and expensive issue

4. Test Approaches There are a number of different testing approaches:
By scope
By purpose
By life-cycle phase
Component testing
Correctness testing
Requirements testing
Module testing
Performance testing
Design testing
Integration testing
Reliability testing
Acceptance testing
System testing
Security testing
Maintenance testing
Testing ‘by scope’ starts at the component level then proceeds through each phase until the final system is tested as a whole
Testing ‘by purpose’ entails the whole reason for testing. It makes sure the program is correct and runs to the original specification
Testing ‘by life-cycle’ phase include the final software development test, acceptance testing where the software is sold to the client

5. Components Components are sometimes called units
They are the building blocks of software applications
They are defined as pieces of software such as sub-routines or procedures that can be compiled and executed on their own
A component will be the work of a single programmer and they will also test the code at a basic, White Box, level

6. Component Testing
With White Box testing component code is seen and it is the workings of the code that are tested
The component can be tested in Static or Dynamic mode
In static mode the component does not require to be executed. A detailed catalogue of reviews and inspections is compiled for each module
Inspections contain a precise framework for rigorously checking component documentation and code
In dynamic testing the component program is executed using test values for normal, extreme and exceptional cases

7. Modules
Modules are a collection of dependant components or procedures designed to be part of the main program
They are not complete programs in themselves, they can not run independently
It often happens that a module becomes ready for testing before the main program. It is common practice to write a small program, called a Driver or Test-Harness to run the module and supply it with test data
Driver programs are commercially available

8. Stubs
A stub is a module that has the appropriate interface but does not contain a lot of code
It might contain no more than a line of code to display what the module will do when its complete
The system as a whole is laid out using stubs to ensure that the overall structure is correct
Stubs are then converted into fully functional modules

9. Module Testing Modules are created and tested within their sub-systems
When all modules have been tested the sub-system as a whole is tested then sub-systems are brought together and the whole program is tested
At system level the type of testing is Black Box Testing
Black box testing takes the program specification as the sole source of test cases
One advantage of this is that developers who test a system can be different from those who create it

10. Module Test Progression
The testing process involves feedback
Testing might indicate errors in a module which would need debugged and tested again
The usual strategy is to test software twice
The module is first tested within the company, this is Alpha Testing
It is followed by Acceptance or Beta Testing

11. Alpha Testing
Alpha testing can be regarded as ‘Does the software work?’
This is the stage in the development cycle where the software is first able to run
This testing takes place on the software developers premises
Alpha testing is done for 2 reasons;
To reassure the clients the software is working
To find errors that can only be found in operational use
Alpha testing is performed on an early version of the code, that might not have all intended functionality
Alpha testing should be conducted with as much independence from the development team as possible

12. Beta (Acceptance) Testing
This is for the client to say ‘yes we will pay for the software’
Beta testing is the highest level of testing in the software development cycle and is done prior to commercial release
It confirms that the program is as near to correct as possible
The software is tested by independent users who log and report back to the development team, this process might be iterative if errors have to be corrected
The functionality delivered in beta test releases might not be the final product

13. Debugging
A bug is a fault in a program that causes it to function abnormally
Debugging is the process of locating and fixing errors
Programs that help to do this are called debuggers
Most software development tools offer debugging tools
Using a compiler the first task of the debugging tool is to link the object code to source code to locate the error
The part of the compiler responsible for this is the Link-Loader

14. Debugging Tools
With the debugging features activated a program will run slower, so it is only used when necessary
Debugging tools usually take the form of:
Dry Runs
Trace Tools
Watch Statements
Break Points

15. Dry Run
Bugs can be difficult to locate and correct, the temptation is to tweak the code until it runs correctly, however this can lead to more errors
If a bug does not become apparent a dry run is conducted
A dry run is based on the listing of the code that the programmer works through manually
A Trace Table is used to store and display program variables as the logic of the algorithm unfolds, the actual output can then be checked against the expected
Dry runs are used for locating logic errors and is only practical for simple programs

16. Pupil task
Name and describe two methods of locating errors in a puzzle software.

17. Answer
Set breakpoints (1) – used to stop execution of the program at predefined point (1)
Trace tables (1) – used to record the contents of a variable during manual execution (1)
Dry run (1) – stepping through each line of code manually recording variables (1)

18. Trace Tools
Some programming languages have TRACE facilities as a debugging feature
Tracing gives access to otherwise invisible information about a program execution allowing the programmer to step through the program line by line and stop at points to examine variable content
More enhanced tools allow investigation of memory locations and the content of the stack
Programs that use large numbers of procedures use the stack to store all their procedure calls
Using trace a program will run slower

19. Program Watch
A watch takes an identifier and displays its values as the program progresses
The programmer steps through the code one line at a time and the variable being traced is display on a watch screen
Many programmers prefer to put in watches in the form of output statements that cause the value of the variable to be displayed at points in a program where a bug exists
A draw back of program watching is the number of lines of code increase as does programming time

20. Breakpoints
A break point is a marker set within the code of a program to halt program execution at a predefined spot
The statement responsible will be highlighted and can be inspected while the program is temporarily interrupted
The program then continues to completion or until another breakpoint is found
Breakpoints are often used with traces

21. Pupil task The project team is ready to beta test the software.
Give two reasons why beta testing is necessary.
(ii) Name the two groups involved at this stage and describe the role of each group.

22. Answers i) • Checks software is reliable on the client’s computer.
• Checks client is happy with software and allows increased
reliability of testing.
• Allows client an opportunity to check that software meets
requirements.
• Allows programmers to observe the clients using the
software determining success of user interface etc.
(ii) • End users − provide feedback
• Programming team − maintenance

23. CASE Tools Computer Aided Software Engineering
It refers to the collection of software programs that are designed to automate the development cycle
The implementation of new systems requires many different complex tasks to be organised and completed correctly and efficiently
Information generated has to be kept in synchronisation
The use of CASE tools eases the task of coordinating these activates from analysis to implementation

24. Computer-Aided Software Engineering (CASE), in the field of
Software Engineering is the scientific application of a set of tools
and methods to a software system which is meant to result in
high-quality, defect-free, and maintainable software products.
It also refers to methods for the development of
information systems together with automated tools that can be
used in the software development process

25. Types of CASE Tools Basic categories of CASE tools are available:
Diagramming tools that represent data models according to system specifications.
Screen and Report Generators for creating system specifications.
Data Dictionaries that contain a history of changes made to a system
Code Generators to be able to generate code from data Diagrams themselves.
Documentation generators that make the code more readable.

26. Development of CASE
Sine the early days of writing software there has been a need for automated tools to help the software developer
As computer became more powerful ad the software that ran on them grew larger and more complex, power tools with increasing functionality were required

27. Categories of CASE Tools
CASE tools can be divided into two main groups
Those that deal with the first three parts of the system development life cycle (preliminary investigation, analysis, and design) and are referred to as Front-End CASE Tools or Upper CASE Tools
Those that deal mainly with the implementation, testing and installation are referred to as Back-End CASE Tools or Lower CASE Tools

28. Upper CASE Tools
These are basically general-purpose analysis and design specification tools
During the initial stages of system development, analysts have to determine system requirements and analyse this information to design the most effective system
Computerised CASE tools allow for changes to be made automatically, very quickly and accurately
Data Dictionaries are data processing systems products that are specifically designed to hold, maintain and organise information
They have facilities for producing a variety of reports
They allow developers to be more productive
The goal of a CASE tool is to refine the analysis and design stages to allow automated production of code, around 75%

29. Data Dictionaries
A data dictionary is an automated tool for collecting and organising detailed information about system components
A data dictionaries main facility is to document data elements, records, programs, files, users etc
They also have the facility to cross-reference all system components and contain details of:
Systems environment
Audit trails
Reports
Forms
Functions
Processes

30. Lower CASE Tools
These focus on the architecture of the system and its implementation and maintenance
These tools are effective in helping with the generation of the program code and are referred to as Code Generators
A code generator is a tool that enables automatic generation of code from the analysis and design specifications
Generating code this way ensures that all code is produced with identical naming conventions

31. Code Generators
Code generators produce a high quality of code that is easy to maintain and is portable
They are able to interact with Upper CASE tools to aid in the development of code

32. Document Generators
A further enhancement to CASE tools is document generators
A document generator is a CASE tool that generates technical documentation from source code comments
The comments that are produced conform to a standard format

33. Object-Oriented CASE
CASE tools are well supported in object-oriented programming systems (OOPS)
Earlier problems with OOPS focussed on models created for software development systems and their different notations
This was overcome by the use of UML, Unified Modelling Language, which is a new standard for producing diagrams and charts
All current CASE tools have now adopted UML for specifying, visualising and constructing software systems

34. UML CASE tools offer automatic code generation from the UML diagram
This tool produces a framework for the code which contains objects and classes. An Executable Prototype is produced
This is an executable source code program obtained directly from UML
One of the main features in UML is Reverse Engineering where existing source code is reversed engineered into a set of UML diagrams

35. RUP Rational Unified Process
In conjunction with UML developers also employ RUP
This is a development process to deliver best practices during each stage of a project
Using RUP risks are lowered during all stages

36. Advantages of CASE Increase Speed
CASE tools provide automation and reduce the time to complete tasks
Increased Accuracy
CASE tools can provide on-going debugging and error checking which is vital for early defect removal
Reduced Costs and Maintenance
Overall system quality improves using CASE. There is also better documentation so the net effort and cost involved is reduced
Better Documentation
Using CASE tools vast amounts of documentation are produced. An important aspect is CASE Repository, this is a developers database with information relating to the projects stored. It can be regularly updated
Better Communication
Information generated from one tool can be passed to another, allowing for important information to be passed efficiently and effectively

37. Limitations Of CASE Tools
Although CASE tools are becoming more popular user can be
subject to some limitations:
Choice
Over 1000 CASE tools exist and choosing one is difficult, a major project in itself
Costs
CASE tools are not cheap. Hardware, software, training and consulting are all factors in the total cost equation
Training
Users need time to learn the technology. A CASE consulting industry has evolved to support uses of CASE tools

38. Pupil task
Describe two benefits of using Computer-Aided Software Engineering (CASE) tools.

39. Answer
• Computerised generation of graphical designs and information shared across the system would be monitored.
• Automated data dictionaries.
• Tools to track dependencies.
Do not allow compilers, editors, debuggers or other software development type answers