CTFL-v4 Fundamentals of Testing Practice Question
Which of the following describes the 'Pesticide Paradox' in the context of software testing?
⚠ Common exam trap
Candidates sometimes confuse this with 'testing is context-dependent' or 'absence of errors fallacy', failing to recognize the specific phenomenon of test repetition leading to reduced effectiveness.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Repeating the same test cases will eventually stop finding new bugs.
The Pesticide Paradox occurs when the same set of test cases is repeatedly executed, eventually becoming ineffective at finding new defects because the software becomes 'immune' to them. This happens because the existing tests only exercise known paths. To remain effective, testers must periodically update and create new, diverse test cases to uncover different types of failures that were not addressed by the original, repetitive testing suite.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Automated tests always find more defects than manual tests over time.
Why it's wrong here
Automation is efficient but not inherently better at finding bugs than manual testing. If automated tests are static and never updated, they will suffer from the Pesticide Paradox just as much as manual tests. The value of automation lies in speed and repeatability, not necessarily in superior defect discovery.
- ✓
Repeating the same test cases will eventually stop finding new bugs.
Why this is correct
The Pesticide Paradox states that if tests are not reviewed and updated, they eventually stop uncovering new defects because the system logic covered by those tests is already verified. New defects often lie in areas not covered by existing tests, requiring the development of new, varied test scenarios.
- ✗
Testing becomes more expensive as the software grows in size.
Why it's wrong here
While testing costs can scale with size, this describes resource management, not the Pesticide Paradox. The paradox specifically refers to the diminishing returns of re-running the same test scripts, not to the overall budget or effort associated with maintaining a large, complex test suite in a growing project.
- ✗
Developers will stop fixing bugs if they are found too frequently.
Why it's wrong here
Developer fatigue is a project management issue, not a fundamental testing concept like the Pesticide Paradox. While frequent bug reports can lead to frustration, the paradox specifically addresses the effectiveness of the test suite itself in catching new bugs, not the behavioral reaction of the development team involved.
About these practice questions
Courseiva writes every CTFL-v4 question from scratch — 144 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISTQB exam blueprint
This CTFL-v4 practice question is part of Courseiva's free ISTQB certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CTFL-v4 exam.