The Art of Perfecting Software

1
The Defect Lifecycle

• The Art of Perfecting Software

2
Remember This?

• Validation and verification of requirements can
  reduce costs by finding defects early in the
  process when they cost less to fix

3
A Word About Development Environment Architecture
4
Faults and Failures

• Fault Developer Error in the Code
• Failure Departure from Required Behavior (User
  Sees Impact)
• A Defect Begins as a Fault

5
Fault Correction and Fault Tolerance

• Fault Correction Eliminate the Fault and Damage
  it Caused
• E.G. halt the application, dump to a log file,
  request user notify the administrator
• Fault Tolerance Isolate Damage Caused by the
  Fault
• E.G. log the anomaly and move on

6
Defect Tracking

• Process by which faults and failures within a
  system are detected, communicated, tracked and
  resolved
• Defects can range from a simple typo in a label
  to a major failure in an algorithm causing system
  failure
• It is best to use some sort of defect tracking
  software to manage defects and there are many
  tools to choose from

7
Detecting Faults

• Active Fault Detection (remember the green check
  marks)?
• Good Design
• Mutual Suspicion assume inputs can be invalid
• Code Reviews
• Unit Tests
• Static Code Analysis
• Compilation Checks/Syntax Checks
• Testing
• Sample Test Plan
• Passive Fault Detection
• Betas
• Users

8
Communicating Defects

• The exact set of information that is tracked will
  vary among different organizations and even
  between projects
• Basic information that should be tracked
• Title
• Description (i.e. Symptoms)
• Steps to Reproduce
• Categorization (e.g. Priority, Severity)
• Status (i.e. Workflow State, See Next Slide)
• Assigned To
• Triage

9
Defect Tracking Process
10
Debugging

• Print Statements vs. Tracing
• Stepping into Code
• Inspecting Variables
• Stack Trace