CS 325: Software Engineering

March 24, 2015

Implementation Considerations• Coding Standards• Pair Programming• Test-Driven Development

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Coding StandardsEstablishing coding standards for a software development process can be contentious, but has several concrete advantages:• Provides a consistent level of code

quality across teams and developers• Facilitates project management, software

integration, software reuse, software maintenance, version control, personnel transfer, code review, and software testing

Enterprise-Level Con-

ventions; 19

Project-Level Conventions;

30Developer-Level Conventions; 10

Probably Use Standards; 3

Hope To Use In Future; 18

Not Consider-ing Use; 13

Don't Know; 8

Coding Standards

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Coding Standards: Indentation

Kernighan & Ritchie Style(from The C Programming

Language)int main(int argc, char *argv[]){ ... while (x == y) { something(); somethingelse(); if (some_error) { do_correct(); } else { continue_as_usual(); } } finalthing(); ...}

int main(int argc, char *argv[]){ ... while (x == y) { something(); somethingelse(); if (some_error) { do_correct(); } else { continue_as_usual(); } } finalthing(); ...}

int main(int argc, char *argv[]) { ... while (x == y) { something(); somethingelse(); if (some_error) { do_correct(); } else { continue_as_usual(); } } finalthing(); ... }

Allman Style(from Eric Allman’s ANSI C

Documentation)

Whitesmiths Style(from first commercial C

compiler)

Many argue that the particular coding standard used is less important than the fact that one is used.

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Coding Standards: Comments• When modifying code, always keep the

commenting around it up to date.

• At the beginning of every routine, it is helpful to provide standard, boilerplate comments, indicating the routine's purpose, assumptions, and limitations. A boilerplate comment should be a brief introduction to understand why the routine exists and what it can do.

• Avoid adding comments at the end of a line of code; end-line comments make code more difficult to read. However, end-line comments are appropriate when annotating variable declarations. In this case, align all end-line comments at a common tab stop.

• Avoid using clutter comments, such as an entire line of asterisks. Instead, use white space to separate comments from code.

• Avoid surrounding a block comment with a typographical frame. It may look attractive, but it is difficult to maintain.

• Prior to deployment, remove all temporary or extraneous comments to avoid confusion during future maintenance work.

• If you need comments to explain a complex section of code, examine the code to determine if you should rewrite it. If at all possible, do not document bad code—rewrite it. Although performance should not typically be sacrificed to make the code simpler for human consumption, a balance must be maintained between performance and maintainability.

• Use complete sentences when writing comments. Comments should clarify the code, not add ambiguity.

• Comment as you code, because most likely there won't be time to do it later. Also, should you get a chance to revisit code you've written, that which is obvious today probably won't be obvious six weeks from now.

• Avoid the use of superfluous or inappropriate comments, such as humorous sidebar remarks.

• Use comments to explain the intent of the code. They should not serve as inline translations of the code.

• Comment anything that is not readily obvious in the code.

• To prevent recurring problems, always use comments on bug fixes and work-around code, especially in a team environment.

• Use comments on code that consists of loops and logic branches. These are key areas that will assist the reader when reading source code.

• Separate comments from comment delimiters with white space. Doing so will make comments stand out and easier to locate when viewed without color clues.

• Throughout the application, construct comments using a uniform style, with consistent punctuation and structure.

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Pair ProgrammingExtreme Programming advocates programming in pairs at one workstation to ensure better focus and stronger oversight.

Unfortunately, this practice sometimes leads to tedium, inequity, or conflict.

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Pair ProgrammingStudies indicate that pairs spend about 15% more time on programs than individuals, but that the resulting code has about 15% fewer defects.By periodically switching between the roles of code-writer to code-reviewer, programmers share knowledge and experience, improve design quality and team communication, and generally express increased job satisfaction.Primary pairing variations:

Expert-Expert: High productivity, low learningExpert-Novice: Good mentoring, potential for intimidationNovice-Novice: Sometimes more productive than novices working independently

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Test-Driven DevelopmentOne variation of extreme programming advocates beginning the implementation by developing tests that the software initially fails and then minimally adding code until the system passes the tests.

E. Clean up code

• Go back to A and repeat

D. Run all tests

• If tests fail, go back to C

C. Write production code

B. Check if

test fails

• If test succeeds, go back to A

A. Write a test

Once the code minimally passes the tests, it is refactored to meet standards, and then the entire process begins again.

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Test-Driven DevelopmentTDD has numerous benefits, including:• Improved design (an emphasis on functionality

needed by users)• More modularized code, more focused classes, and

looser coupling• Fewer defects in final, delivered codeTDD also has a few drawbacks, including:• Emphasis on unit testing, neglecting integration or

system testing• GUIs, databases, network configurations require

full functional testing• Management may not support testing at the

expense of coding