Nine Steps to Delivering Defect-Free Software

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Nine Steps to Delivering Defect-Free Software

• By Terence M. Colligan
• Presented by Isaac Bailey

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Outline

• Introduction
• 1. Believe Defect-Free Software is Possible
• 2. Think Defect-Free Software is Important
• 3. Commit to Delivering Defect-Free Software
• 4. Design Your Code for Simplicity and
  Reliability
• 5. Trace Every Line of Code When Written
• 6. Review Code by Programmer Peers
• 7. Build Automated QA into Your Code
• 8. Build and Test Daily
• 9. Use Automated Checking Wherever Possible
• Summary

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Introduction

• Terence Colligan has been working in software
  development for 30 years at the time this article
  was written.
• One engineer changed his entire outlook on how
  software should be written.
• They have come up with these nine steps.

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1. Believe Defect-Free Software is Possible

• The first reaction is Its just not possible.
• This attitude is the biggest obstacle.
• The average engineer
• Defects are inevitable.
• The defect-free engineer
• Defects embarrass them.
• They are disgusted to find defects in other
  peoples code

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2. Think Defect-Free Software is Important

• Why is defect-free software important?
• Reduces support costs.
• Reduces programming costs.
• Reduces development time.
• Can provide a competitive advantage.

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3. Commit to Delivering Defect-Free Software

• Colligan used to make decisions based on short
  schedule time instead of focusing on the
  defect-free side.
• In reality the schedules were longer, there were
  more bugs in the software, more support was
  required, higher costs and lower profits.

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4. Design Your Code for Simplicity and
Reliability

• A clean, well structured design simplifies
  producing reliable code. Whereas a poor design
  cripples the engineer.
• Each function should be precise and have only one
  purpose.
• If a bug is found then the programmer can find
  and fix the code fast, saving time and money.

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5. Trace Every Line of Code When Written

• Using a debugger trace every new line of code.
• Try to predict the outcome before each line is
  executed.
• By stepping through each line of code, you ensure
  that the new code is fully tested.
• You confirm that the code is functioning as
  intended.

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6. Review Code by Programmer Peers

• Single most cost-effective way to remove bugs
  from code.
• This process forces the engineer to articulate
  assumptions.
• Allows for more than one engineer to view the
  code while it is still easy to change.
• Encourages cross-training and sharing of
  techniques.

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7. Build Automated QA into Your Code

• Automated test are designed to exercise every
  part of the program.
• Use the power of the computer.
• Avoid human error.

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8. Build and Test Daily

• This gives developers feedback about changes made
  and management gets objective feedback about the
  project status.
• This helps in making better estimates about costs
  and shipping dates.

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9. Use Automated Checking Wherever Possible

• Set your compilers warning level to maximum.
• Use the memory trace subsystem.
• Other commercial tools

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Summary

• It take a lot of work.
• Some details will be adapted to your situation.
• By demanding defect-free software you can deliver
  it.

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• http//www.tenberry.com/errfree/steps.htm