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ISEB-SWTINT1 · Question #47

Scenario 1 A computerised system is being created to monitor the life support system on board a submarine. It monitors air quality, water supplies and temperature. This system will be supplied and…

The correct answer is D. Boundary Value Analysis. Boundary Value Analysis (BVA) is correct because the requirement for oxygen release is inherently threshold-driven - oxygen must be released when its percentage falls to a critical level, making the exact boundary values (e.g., the minimum acceptable O₂ percentage, just above…

Test Techniques

Question

Scenario 1 A computerised system is being created to monitor the life support system on board a submarine. It monitors air quality, water supplies and temperature. This system will be supplied and maintained by SubsInc. SubsInc uses the V-model for software development and conducts four levels of testing, from unit through to operational and site acceptance testing. Two key risks identified for the air quality system are: 1. If the percentage of oxygen in the air falls too low, personnel may suffocate 2. If the concentration of carbon dioxide in the air rises too high, the air may become toxic. To address these risks, the requirement specification for this system includes the following requirements: R1) Oxygen must be replaced as it is consumed. R2) Carbon dioxide must be removed from the air. These requirements must be reflected in the functional, technical and program specification documents. You are a newly recruited test manager. Which of the following test design techniques would be most suitable for testing that the oxygen is released at the required times?

Options

  • ADecision Testing.
  • BStatement Testing.
  • CData flow Testing.
  • DBoundary Value Analysis.

How the community answered

(28 responses)
  • A
    14% (4)
  • B
    7% (2)
  • C
    4% (1)
  • D
    75% (21)

Explanation

Boundary Value Analysis (BVA) is correct because the requirement for oxygen release is inherently threshold-driven - oxygen must be released when its percentage falls to a critical level, making the exact boundary values (e.g., the minimum acceptable O₂ percentage, just above it, and just below it) the most important points to test. BVA specifically targets these edges where behavior changes, which is precisely where bugs in life-critical systems are most dangerous.

Why the distractors are wrong:

  • A (Decision Testing) verifies that all true/false branches in the code are exercised, but it doesn't focus on which specific values trigger those branches - it would miss off-by-one errors at the oxygen threshold.
  • B (Statement Testing) simply ensures every line of code executes at least once; it reveals untested code paths, not whether the system responds correctly at critical concentration levels.
  • C (Data Flow Testing) tracks how variables are defined, used, and killed through the program - useful for detecting stale or undefined data bugs, but not suited to validating trigger conditions at specific values.

Memory tip: BVA = "at what number does behavior change?" Anytime a requirement says something must happen when a value reaches a level (oxygen too low, CO₂ too high, temperature out of range), that's a boundary - reach for BVA.

Topics

#boundary value analysis#air quality monitoring#numeric ranges#test technique selection

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