You are reviewing the testability of your SUT. Which of the following BEST refers to the characteristic of OBSERVABILITY?

Question

Options

• AThe ability of the SUT to perform its intended function for a specified period of time
• BThe ability to exercise the SUT by entering inputs, triggering events and invoking methods
• CThe ability of the SUT to prevent unauthorized access to its components or data.
• DThe ability to identify states, outputs, intermediate result and error messages in the SUT

• A
  86% (30)
• B
  3% (1)
• C
  3% (1)
• D
  9% (3)

Explanation

There appears to be an error in the marked answer. Option D is actually the correct answer for Observability, not A.

Observability refers to how easily a tester can inspect the internal states, outputs, intermediate results, and error messages of the SUT during testing - option D matches this definition exactly. If you can't "see" what the system is doing internally, defects are much harder to detect and diagnose.

Why the distractors are wrong:

• A describes Reliability - the ability to function correctly over a period of time, which is a quality attribute, not a testability characteristic.
• B describes Controllability - the ability to drive or stimulate the SUT with inputs and events (the complementary characteristic to observability).
• C describes Security - access control has nothing to do with testability characteristics.

Memory tip: Think of Observability and Controllability as a pair - Control is the input side (you push things in), and Observe is the output side (you look out). If you can control and observe a system fully, it's highly testable. The acronym SOCS (Simplicity, Observability, Controllability, Self-describedness) can help you recall the key testability characteristics.

Note for exam takers: If your exam source lists A as correct, double-check your study material - this is likely a typo or formatting error in the question bank.

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