ISTQB CTAL-TTA Exam With Confidence Using Practice Dumps

To achieve 100% decision coverage, we need to ensure that every decision (if statement) in the code has been tested for both true and false outcomes. Let's analyze the code and count the decisions:

IF (Room_price > 200)

IF (Loyalty_level = Platinum) inside Room_price > 200

ELSE within the same decision above

IF (Loyalty_level = Gold) inside the ELSE of decision 2

IF (Room_price > 150)

IF (Loyalty_level = Platinum) inside Room_price > 150

ELSE within the same decision above

IF (Discount_factor < 100%)

To cover all these decisions, we need test cases for each possible combination:

Room_price > 200 and Loyalty_level = Platinum.

Room_price > 200 and Loyalty_level = Gold.

Room_price > 200 and Loyalty_level not Platinum or Gold.

Room_price <= 200 and Room_price > 150, and Loyalty_level = Platinum.

Room_price <= 200 and Room_price > 150, and Loyalty_level not Platinum.

Room_price <= 150.

From these scenarios, we can see that the minimum number of test cases required to achieve 100% decision coverage is four:

Test with Room_price > 200 and Loyalty_level = Platinum (tests decision 1 true, 2 true, and 8 true).

Test with Room_price > 200 and Loyalty_level = Gold (tests decision 1 true, 2 false, 4 true, and 8 true).

Test with Room_price > 200 and Loyalty_level not Platinum or Gold (tests decision 1 true, 2 false, 4 false, and 8 true).

Test with Room_price <= 200 and Room_price > 150, and Loyalty_level = Platinum (tests decision 1 false, 5 true, 6 true, and 8 true).

Test with Room_price <= 200 and Room_price > 150, and Loyalty_level not Platinum (tests decision 1 false, 5 true, 6 false, and 8 true).

Test with Room_price <= 150 (tests decision 1 false, 5 false, and 8 false).

Given that these six cases test all branches, four test cases are required to ensure that all decisions are covered at least once.

Therefore, the correct answer is A. 4.

In the context of software testing, different safety integrity levels (SIL) require different levels of rigor in testing. According to the IEC61508 standard, for software components rated at SIL 2, achieving 100% statement coverage and 100% decision coverage is recommended. Statement coverage ensures that every line of code is executed at least once during testing, while decision coverage ensures that every decision in the code (e.g., every branch of an IF statement) is executed on both the true and false sides. These coverage criteria ensure a thorough testing of the software components to validate that they behave correctly in all circumstances. Multiple condition coverage and MC/DC coverage (Options A and B) are more rigorous and typically required for higher SIL levels, such as SIL 4.

For a Medium risk mission- or safety-critical system, the best testing approach includes a combination of automated tests, exploratory tests, and manual black-box tests. Option B is the most comprehensive, advocating for automated tests to ensure reliability and repeatability, highly recommending exploratory tests to cover unforeseen scenarios, and recommending manual black-box tests to cover standard use cases. This multifaceted approach ensures thorough testing coverage essential for medium risk, safety-critical systems​​.