ISTQB - International Software Testing Qualifications Board White-Box Test Design Questions and Answers

Question 1

A developer has written the following pseudocode. What is the MINIMUM number of test cases required to achieve 100% statement coverage?

READ A
READ B
IF A > B THEN
  PRINT A
ELSE
  PRINT B
ENDIF

Accepted Answer

2

Answer

To achieve 100% statement coverage, every executable statement in the code must be exercised at least once. In this pseudocode, one test case where A > B (e.g., A=10, B=5) will execute the `PRINT A` statement. A second test case where A is not greater than B (e.g., A=5, B=10) is required to execute the `PRINT B` statement. Therefore, a minimum of two test cases are needed to cover all executable statements.

Question 2

Which of the following BEST defines Decision Coverage?

Accepted Answer

It ensures that every possible outcome (TRUE and FALSE) of each decision point in the code has been exercised at least once.

Answer

Decision coverage, also known as branch coverage, is a white-box testing technique that aims to exercise every possible outcome of a decision point (e.g., an IF statement or a loop condition) at least once. This means testing both the TRUE and FALSE branches for each decision.

Question 3

Which of the following statements about the relationship between statement coverage and decision coverage is correct?

Accepted Answer

Achieving 100% decision coverage guarantees 100% statement coverage.

Answer

If you achieve 100% decision coverage, you have tested both the TRUE and FALSE outcomes of every decision. By doing so, you will have inherently executed all the statements within those decision branches. However, the reverse is not true; achieving 100% statement coverage does not guarantee 100% decision coverage, as a test might execute all statements without testing all possible decision outcomes.

Question 4

What is the primary goal of Modified Condition/Decision Coverage (MC/DC), a technique often required for safety-critical systems?

Accepted Answer

To show that each condition within a decision can independently affect the outcome of that decision.

Answer

The goal of MC/DC is to demonstrate that each individual condition within a complex decision can, on its own, affect the decision's outcome. This is achieved by creating test pairs where only one condition's value is changed, and this change causes the decision's outcome to flip, proving the independence of that condition.

Question 5

A tester is using white-box test design techniques. In which of the following areas are these techniques MOST effective for finding defects?

Accepted Answer

Uncovering logic errors and incorrect assumptions in the code's control flow.

Answer

White-box testing is based on the internal structure and implementation of the code. Its primary strength lies in systematically exercising the code's logic, paths, branches, and conditions to find errors in the control flow, such as unreachable code, logic errors in loops and conditional statements, and incorrect data flow. Black-box techniques are better suited for finding issues related to requirements, usability, and business needs.

ISTQB - International Software Testing Qualifications Board Practice Test

ISTQB - International Software Testing Qualifications Board Practice Test

ISTQB - International Software Testing Qualifications Board White-Box Test Design Questions and Answers