CSC/ECE 517 Fall 2011/ch6 6f jd

Continous Integration

Introduction

Definitions

Time To Response (TTR)

Test-Driven Development (TDD) is the process of writing tests first and foremost. These tests represent desired improvements and/or new functionality in the system. Since these changes have yet to be implemented, the tests must fail when initially run. Then code is written until these tests can be passed, assuring that the desired behavior is exhibited by the code. Finally the code is rewritten to meet acceptable standards.

Why Implement CI?

Most of the major companies producing software for sale are in the business to make money. Companies have discovered that the best way to make money is decrease the number of defects going out to customers. Tons of research has been done on how to make quality software with fewer defects. The usual cost of fixing a defect slipping from one phase to next phase increases by ten times. So for example if a defect cost $60 to fix during the coding phase will cost $600 if found during validation testing. Moreover if a defect is shipped along with the product to the customers it can certain times cost millions of dollars. Additionally these small defects can have big impact on company’s reputation. Below are some examples which shows how small defects when slipped or goes out undetected can cost millions of dollars.

1. In 2007 a single faulty piece of embedded software, on a network card, sends out faulty data on the United States Customs and Border Protection network, bringing the entire system to a halt. Nobody is able to leave or enter the U.S. from the LA Airport for over eight hours. Over 17,000 planes were grounded for the duration of the outage resulting in millions of dollars in damage.
2. A forgotten error handling statement which caused the famous ping of death also known as blue screen in 1995. A lack of error handling in the IP fragmentation reassembly code makes it possible to crash many Windows, Macintosh, and Unix operating systems by sending a malformed “ping” packet from anywhere on the Internet.
3. In 2004, EDS software giant introduced a large, complex IT system to the U.K.’s Child Support Agency (CSA). At the exact same time, the Department for Work and Pensions (DWP) decided to restructure the entire agency. The restructure and the new software were completely incompatible, and irreversible errors were introduced as a result. With over 500 bugs still reported as open in the new system, the clash of the two events has crippled the CSA’s network. As a result the system somehow managed to overpay 1.9 million people, underpay another 700,000, had $7 billion in uncollected child support payments, a backlog of 239,000 cases, 36,000 new cases “stuck” in the system, and has cost the UK taxpayers over $1 billion to date.

The above examples show why testing phase is as important as coding phase. The more you test the better the software becomes as fewer and fewer defects are found. Below are some of the reasons why big companies are leaning more towards adopting agile and CI for software development.

1. Many developers work on a software through multiple agile teams. Though the focus of each agile team is a specific module of the software but it is important to make sure the overall integrity of the system is always correct.
2. One of the main benefits of agile project development is to have a shippable product at the end of each sprint. If testing is kept until the end than you can’t have a shippable product at the end of each sprint. You have to have some automated testing that can test this functionality on daily basis.
3. The other problem that used to occur by following traditional software development was that management did not know the exact status of the product which includes the number of bugs in the system until the validation phase. This can cause problem in releasing software on time. CI gives an option to generate various reports to solve these kinds of problems and to give management early indication if the product release can be done on time.
4. The main reason for using CI is to cut down on validation cost by finding the bugs early during coding phase.
5. CI infrastructure provides way to decrease Time to Response (TTR) for fixing defects.
6. Additionally some CI infrastructure provides valuable tools like build management and build acceleration. With build acceleration developers and QA do not have to wait long periods to get a completed builds. Build acceleration decreases the build time by performing non-dependent tasks in parallel resulting in increased productivity.

References

• [1] Software Bugs Top Ten Software Bugs
• [2] Electric Cloud Electric Commander

Expand your knowledge

• Continuous Integration Wikipedia CI