CTFL 3.1.2: Explain the value of static testing

• a
  It confirms the software behaves correctly in its target environment before releaseConfirming behaviour in an environment requires execution, which static testing does not do.
• ✓
  Correct answer: It detects defects in the earliest phases of the SDLC, fulfilling the principle of early testingDetecting defects in the earliest phases fulfils the principle of early testing.
• c
  It measures quality characteristics that depend on executing the code, such as performance efficiencyCharacteristics that depend on executing the code are measured by dynamic testing.
• d
  It identifies the failures the software produces, so the underlying defects can be analysedCausing failures and analysing back to the defect is how dynamic testing works.

Static testing can detect defects in the earliest phases of the SDLC, fulfilling the principle of early testing, and can identify defects that dynamic testing cannot find at all. The other three options describe dynamic testing: confirming behaviour in the target environment, measuring characteristics that depend on executing code, and working back from failures to the defects behind them.

Syllabus section 3.1.2

• a
  A memory leak that only appears after hours of operationA memory leak appears at runtime over time and needs dynamic testing to surface.
• b
  Slow response times under peak loadSlow response under load is runtime behavior found by dynamic performance testing.
• ✓
  Correct answer: A requirement that contradicts another requirement in the same specificationContradictory requirements are found directly in the document by static testing.
• d
  A failure that occurs only on a specific mobile deviceA device-specific failure manifests at runtime and requires dynamic testing.

Static testing excels at finding defects directly in work products: contradictory or ambiguous requirements, design flaws, unreachable code, and deviations from standards. Runtime behavior such as performance or device-specific failures requires dynamic testing.

Syllabus section 3.1.2

• a
  Dynamic testing will find the same defects later, so the total effort stays the sameSome defects found statically cannot be detected by dynamic testing at all.
• b
  The overall project cost will rise, because the reviews themselves cost time and effortReviews do cost effort, but overall project costs are usually much lower with them.
• c
  Defects will be found at the same rate as before, but earlier in the scheduleStatic testing finds defect types dynamic testing cannot, so the rate is not unchanged.
• ✓
  Correct answer: Fewer defects will reach design and code, and less effort will go into fixing them laterFewer defects propagate onward, and less effort is spent fixing them later.

Even though reviews can be costly to implement, overall project costs are usually much lower than when no reviews are performed, because less time and effort needs to be spent on fixing defects later in the project. Static testing also finds defect types that dynamic testing cannot detect at all, so the defects are not simply found later by another means.

Syllabus section 3.1.2