Unit 6 - Software Design and Development LESSON 8 QUALITY ASSURANCE

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1 Unit 6 - Software Design and Development LESSON 8 QUALITY ASSURANCE

2 Previously Key features of programming languages Software Development Lifecycle Design models Some software structures functions, procedures, classes and objects; abstraction of data; pre-defined code. Guess the number game

3 What is covered in this session More software structures readability e.g. comments, appropriate names for variables, indentation; quality of code e.g. efficiency, reliability, robustness, usability, portability, maintainability.

4 Code Readability part of the development process, adding comments doing code inspections can identify blocks of code which would benefit from being refactored.

5 Code Readability Analyst programmers usually work within guidelines set out in a standards manual including: adding comments to all code files using meaningful names for variables and procedures. the use of Hungarian notation or use of camel case. make it easier for another developer to understand the logic. reduces maintenance costs, a key requirement for any business. contributes to the quality of the code makes the code more efficient.

6 Hungarian notation Naming convention for identifiers the name of a variable or function indicates its type or intended use Systems Hungarian notation prefix=actual data type e.g. laccountnum (long integer) Apps Hungarian notation Logical data type e.g. strname (string of unknown data type) Language independent good practice Named for Charles Simonyi ("Simonyi Károly )

7 Refactoring restructuring (rearranging) code in a series of small, semantics-preserving transformations (i.e. the code keeps working) in order to make the code easier to maintain and modify. Refactoring is not just arbitrary restructuring Code must still work. Small steps only so the semantics are preserved (i.e. not a major re-write). Unit tests to prove the code still works

8 When to refactor Any time that there is a better way to do things. Better means making the code easier to understand and to modify in the future. can do so without breaking the code. Unit tests are essential for this. You should not refactor: Stable code that won t need to change. Someone else s code, unless the other person agrees to it or it belongs to you Not an issue in Agile Programming since code is communal.

9 Code Readability Code indentation shows the hierarchical structure of the code. Visual studio will auto indent your code as you develop the program.

10 Indentation Makes code easier to read! Might be essential to syntax (eg Python)

11 Comments What does this bit of code do? Remind the author Inform subsequent developers/maintainers Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live Quoted by Martin Golding 1994, original author unknown

12 Task 23 Using the OOP payroll (Wiki lesson 9): Add suitable comments to the code to improve the quality. Note any indentation Are the variables appropriately named using Hungarian notation or camelcase? Can you refactor any code? 30 mins

13 Quality The degree to which the software satisfies stated and implied requirements. Absence of system crashes. Correspondence between the software and the users expectations. Performance to specified requirements.

14 Quality Lack of Quality lowers production speed, increases maintenance costs can adversely affect business.

15 Quality Assurance Plan Should be in writing. Decide if a separate group should perform the quality assurance activities. Should include: defect tracking, unit testing, source-code tracking, technical reviews, integration testing system testing. structured walk throughs.

16 Quality Assurance Plan Defect tracing keeps track of: each defect found, its source, when it was detected, when it was resolved, how it was resolved, etc. Unit testing each individual module is tested. Source code tracing step through source code line by line. Technical reviews completed work is reviewed by peers. Integration testing -- exercise new code in combination with code that has already been integrated. System testing execution of the software for the purpose of finding defects.

17 Reliability Does the program run accurately and produce the expected results time after time? Autopilot on aircraft Windows safely-remove hardware function does not always work

18 Robustness What happens when users misuse the system? e.g. A user enters data which is out-of-range Does the system return an error message? Sorry you can t do that, try again. Does it crash? Does it return an invalid result?

19 Non-robust code (Java) int var1, var2, var3; var1 = ; var2 = ; var3 = var1 + var2; System.out.println("var3=" + var3); Adds 2 integers, result is also an integer (~3.1 billion) Max value for an integer is ~2.1 billion Java returns: var3= Code from Michael Horowitz, 2007:

20 Usability Is the programme intuitive? Are controls clearly labelled? Are they logically arranged? In order of use Grouped by function

21 Portability Applications/programs than can run on different platforms are said to be portable. Have written programs using Visual Basic.net What platforms are able to run these programs? any platform that can run Microsoft.net. Is VB.net portable then?

22 Portability Ideal is to develop in a language that can run on any platform. Java was designed from the start to be multiplatform, truly portable and this is one reason why it is very popular with developers. So why do we not all develop in Java? (see robust!) Top result on Google: Limitations of Java tml Last updated 06/04/1996

23 Maintainability Updates Bug fixes New features Helped by: Documentation Readability of code Comments Naming of variables Indentation

24 Code quality Task 24 Produce a slide for each of the following explaining what each term means in terms of design and programming code. 1. Reliability. 2. Robustness. 3. Usability. 4. Portability. 5. Maintainability.

25 Summary Code readability. Refactoring code. Quality assurance Code reliability.

26 Assignment 2: submit to Turnitin L3U06A2PeterPan2017 Prepare a presentation, using a given scenario to illustrate it, which will explain where software design and structures fit into the systems development lifecycle (determination of scope, requirements gathering and specification, design, code, test, maintain). Using the scenario identify structures that would be required (functions, procedures, classes and objects; abstraction of data; pre-defined code). Select which software development model (sequential or iterative) would be appropriate for this task and explain why. The scenario is taken from from The Oxford Brookes University asked Alberon to develop a web based system for competency assessment.

27 Assignment 2: submit to Turnitin L3U06A2PeterPan2017 Write an illustrated report of not more than 500 words to explain the importance of creating program code which is of high quality. Describe how the code quality can be improved. All the quality issues mentioned in the unit content (efficiency, reliability, robustness, usability, portability, maintainability) should be covered. The report should explain why the quality issues described may be important in a particular project. Examples of the methods for improving the quality of program code should be included. A table with appropriate headings might facilitate this description.

28 Assignment 2: submit to Turnitin L3U06A2PeterPan2017 Develop your report to discuss the ways in which a programmer can make codes easier to read. Include examples of the methods for improving the readability of program code (e.g. comments, appropriate names for variables and indentation). This additional section should be no more than a further 500 words. A simple description of how to make a program more easily readable is not sufficient. The issues involved, the benefits and drawbacks of each technique should be discussed, giving examples of actual code. Explain what problems may arise if the technique is not used.