CTFL-v4 Fundamentals of Testing Practice Question
Exhibit
LOG_ENTRY: [2023-10-12 14:00:01] ERROR: NullPointerException in PaymentGateway.process() LOG_ENTRY: [2023-10-12 14:00:05] WARN: Database connection latency spike detected (800ms) LOG_ENTRY: [2023-10-12 14:00:10] INFO: User redirected to error page.
Refer to the exhibit. A tester observes these logs during a load test. How does this relate to the 'Testing shows the presence of defects' principle?
⚠ Common exam trap
Candidates incorrectly assume that passing a rigorous load test proves the software is entirely bug-free and will never fail in production.
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
✓
The test identified a defect but does not guarantee the absence of other defects.
This exhibit demonstrates that testing reveals specific failure points under load. The defect (NullPointerException) was triggered by a specific condition (latency). This principle is crucial because it reminds us that while we can observe defects, we cannot state that other, non-triggered paths are error-free. It highlights the importance of environmental monitoring and dynamic analysis in uncovering issues that only surface under stress, reinforcing the need for continuous, context-aware testing strategies.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The test successfully proved that no other defects exist in the PaymentGateway.
Why it's wrong here
Discovering a NullPointerException does not imply the rest of the PaymentGateway module is defect-free. Software complexity often hides other dormant bugs that are not exercised by this specific load test scenario. Claiming the rest of the system is clean is a dangerous assumption that ignores the principle of testing.
- ✗
The test confirms that the system is not capable of handling any production load.
Why it's wrong here
A single failure during a load test indicates a specific defect, but it does not necessarily mean the entire system is incapable of production. It suggests that the system requires tuning or bug fixing. Concluding that the system is entirely unfit is an overgeneralization that ignores potential successful components.
- ✓
The test identified a defect but does not guarantee the absence of other defects.
Why this is correct
Finding a defect confirms the principle that testing shows the presence of bugs. However, it does not confirm the absence of others. The logs capture one failure instance; there could be memory leaks or race conditions occurring simultaneously that were not explicitly logged or triggered by this test run.
- ✗
The test proved that the database latency caused the NullPointerException.
Why it's wrong here
While the logs show a correlation between latency and the error, the test does not provide definitive proof of causation. The NullPointerException might be independent of the database spike. Correlation is not causation, and further investigation is required to determine if the latency is the actual root cause.
About these practice questions
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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.