External Failure
An external failure is a failure experienced by customers or end users after the software has been released into its operational environment.
“A failure that occurs during the regular operation of a system after its delivery to the end users.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is External Failure?
External failures often result in customer dissatisfaction, business disruption, support costs, and damage to an organization's reputation.
Production occurrence: Failures happen after release.
Business impact: External failures may affect users, revenue, or compliance.
Quality improvement: Analyzing failures helps prevent recurrence.
Real World Example
A hospital medication system shows a different dosage warning in test than the one specified by the clinical safety rule.
The team needs precise language to separate what was observed, what should have happened, and whether the difference represents a reportable issue. External failure provides that distinction.
The tester records the steps, data, observed behavior, expected behavior, and evidence so triage can focus on patient safety impact instead of vague descriptions.
The issue is handled faster because External failure helps everyone discuss the problem using a shared testing vocabulary.
Practice Questions
Question 1
Which statement BEST describes External failure in the context of ISTQB terminology?
Question 2
A tester needs to explain External failure to a non‑technical stakeholder. Which approach is MOST appropriate?
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