Which of the following metrics could suggest, under certain condition that an automated regression test suite has NOT been updated for new functionalities added to the SUT?

Question

Options

• AThe ratio of comments to executable statements in the SUT code.
• BThe SUT code coverage provided by the execution of the regression test suite.
• CThe defect density in the automation code of the regression test suite.
• DThe ratio of commands to executable statements in the automation code of the regression test

• A
  4% (1)
• B
  4% (1)
• C
  86% (24)
• D
  7% (2)

Explanation

Defect density in the automation code (C) is the correct answer because when new functionality is added to the SUT without corresponding updates to the regression suite, the existing automation code begins to break - referencing outdated interfaces, incorrect expected values, or removed behaviors. This results in a measurable spike in defects within the test code itself, signaling that the suite has fallen out of sync with the SUT.

Why the distractors are wrong:

• A (comment-to-code ratio in SUT): Reflects documentation habits in the production code - completely unrelated to test coverage of new features.
• B (SUT code coverage): Seems intuitive, but code coverage measures execution paths, not behavioral validation. New code may accidentally be executed by old tests without those tests actually verifying the new functionality - giving a false sense of completeness.
• D (command-to-statement ratio in automation code): Describes structural density of the test code, not whether it targets new SUT capabilities.

Memory tip: Think "Stale tests rot." When the SUT evolves but the test suite doesn't, the automation code starts accumulating bugs (defects) from the mismatch - so high defect density in automation = test suite left behind.

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