Test Case Explosion
Test case explosion is the rapid growth in the number of test cases caused by increasing combinations of inputs, configurations, or conditions.
“The disproportionate growth of the number of test cases with growing size of the test basis, when using a certain test design technique. Test case explosion may also happen when applying the test design technique systematically for the first time.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Test Case Explosion?
Without effective test design techniques, the number of possible test cases can become impractical to execute and maintain.
Combinatorial growth: Test combinations increase rapidly.
Efficiency challenge: Exhaustive testing becomes impractical.
Optimization: Test design techniques help reduce unnecessary cases.
Real World Example
A regulated product team is preparing a release where Test case explosion appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Test case explosion 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 Test case explosion and similar ideas.
The page becomes useful in practice because Test case explosion is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which statement BEST describes Test case explosion in the context of ISTQB terminology?
Question 2
A tester needs to explain Test case explosion to a non‑technical stakeholder. Which approach is MOST appropriate?
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