CTFL-v4 Test Analysis and Design Practice Question
You are designing test cases for a login module. The requirement states: 'Username must be 5-15 characters, alphanumeric only.' Using equivalence partitioning, which of the following is a valid set of test inputs?
⚠ Common exam trap
Candidates frequently fail to include enough invalid partitions, such as boundary values just outside the range or incorrect character types, focusing only on the valid range.
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
✓
User1 (valid), User (4 chars), UsernameTooLongForSystem (20 chars), User@ (invalid char)
Equivalence partitioning divides the input domain into valid and invalid sets to reduce the number of test cases. A valid partition covers the 5-15 length range with alphanumeric characters, while invalid partitions cover lengths <5, lengths >15, and non-alphanumeric characters. Selecting representative values from each ensures complete coverage of both successful flows and error handling logic, confirming the system correctly validates user inputs according to business requirements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
User1 (valid), User (4 chars), UsernameTooLongForSystem (20 chars), User@ (invalid char)
Why this is correct
This set covers the valid partition and three distinct invalid partitions. By testing a value within the range, one below the minimum, one above the maximum, and one with a special character, you effectively exercise all the identified equivalence classes, ensuring the validation logic behaves correctly for all specified input conditions.
- ✗
User1 (valid), User2 (valid), User3 (valid)
Why it's wrong here
This set only tests the valid partition. Equivalence partitioning requires that you test both valid and invalid partitions to verify that the system rejects improper input. Testing only valid inputs leaves the system vulnerable to defects where invalid input might bypass security checks or cause the application to crash unexpectedly.
- ✗
Admin1, User123, Guest9
Why it's wrong here
These are all examples of valid inputs that fall within the 5-15 character range. Testing only these values provides no insight into how the system handles length violations or invalid characters, which are common failure points in login modules that require strict adherence to character and length constraints.
- ✗
User@, Name!, Test$
Why it's wrong here
These inputs only focus on the invalid character partition. While this helps verify that the system rejects special characters, it fails to verify that the system accepts valid alphanumeric strings or handles length-based validation. A complete test design must include representatives from all identified partitions, both valid and invalid.
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.