Phase Containment
Phase containment is the practice of detecting and correcting defects within the same development phase in which they were introduced.
“The policy of removing defects in the same phase of the software development lifecycle in which they were introduced.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Phase Containment?
Finding defects early reduces correction costs, minimizes rework, and prevents defects from propagating into later phases of development.
Early detection: Defects are removed before progressing to the next phase.
Cost reduction: Earlier fixes require less effort and expense.
Quality improvement: Reviews and testing support effective phase containment.
Real World Example
A regulated product team is preparing a release where Phase containment appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Phase containment as interchangeable with nearby ISTQB terms. That makes test scope blurry and can lead to weak evidence for the release decision.
The tester anchors the discussion in the official definition, asks where the concept appears in the product, and designs examples that show the difference between Phase containment and similar ideas.
The page becomes useful in practice because Phase containment is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which statement BEST describes Phase containment in the context of ISTQB terminology?
Question 2
A tester needs to explain Phase containment to a non‑technical stakeholder. Which approach is MOST appropriate?
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