← Back to Home

Root Cause Analysis (RCA)

Root Cause Analysis (RCA) is a systematic approach used to identify the underlying cause of defects, rather than just addressing the visible symptoms.

RCA answers: “Why did this defect happen in the first place?”

1. Definition

Root Cause Analysis (RCA) is a systematic approach used to identify the underlying cause of defects, rather than just addressing the visible symptoms.

RCA answers: “Why did this defect happen in the first place?”

2. Purpose of RCA

  • Prevent recurrence of defects
  • Improve overall process quality
  • Identify gaps in requirements, design, or testing
  • Reduce cost of defects over time

3. When RCA Is Performed

  • For critical or high-severity defects
  • For recurring or production defects
  • After major releases
  • During retrospectives or post-mortems

4. Common Root Cause Categories

  • Requirement issues (ambiguous, missing, incorrect)
  • Design issues (poor architecture, missing validations)
  • Coding issues (logic errors, missed edge cases)
  • Testing gaps (missing scenarios, inadequate coverage)
  • Environment issues (config mismatch, data problems)
  • Process issues (time pressure, poor communication)

5. Manual Tester’s Role in RCA

  • Provide defect details and reproduction steps
  • Identify missed test scenarios
  • Map defects to STLC phases
  • Suggest preventive actions
  • Participate in RCA discussions

6. Common RCA Techniques (Conceptual)

6.1 5 Whys Technique

Ask “Why?” repeatedly until the root cause is found.

Example:

  • Why did payment fail?
  • Because validation failed.
  • Why validation failed?
  • Because requirement was unclear.

6.2 Fishbone (Ishikawa) Diagram

Categorizes causes under:

  • People
  • Process
  • Technology
  • Environment

7. RCA vs Defect Fixing

Aspect RCA Defect Fix
Focus Prevention Correction
Timing Post-incident Immediate
Outcome Process improvement Code change

8. Real-Time Example

Defect: Wrong tax calculation

  • Root cause: Incorrect business rule interpretation
  • Preventive action: Better requirement review and decision tables

9. Common Mistakes

  • Blaming individuals instead of process
  • Performing RCA only for production defects
  • Not implementing preventive actions

10. Interview-Ready Answers

Short answer:

Root Cause Analysis identifies the underlying cause of defects to prevent recurrence.

Detailed answer:

RCA is a structured process used to analyze defects and determine their fundamental cause, enabling teams to improve processes and avoid similar issues in the future.

11. Key Takeaway

RCA shifts focus from fixing bugs to fixing the process that creates bugs.