Which of the following statements about testing in the context of an agile (iterative-incremental) development...

In the context of agile (iterative-incremental) development models, testing is integrated into the development process and occurs continuously throughout the lifecycle of the project. Agile testing emphasizes adaptability and the need for feedback at various stages of development.

Option C is correct because regression testing is indeed necessary whenever a new increment is added to the existing system. Agile development often involves frequent changes and additions to the codebase, which can potentially introduce new defects into previously tested code. Regression testing ensures that new changes have not adversely affected existing functionality.

Options A, B, and D present misconceptions about agile testing:

A is incorrect because, in agile, all types of testing (unit, integration, system, acceptance) are important and occur throughout the iteration, not just unit and acceptance tests.

B is incorrect because agile methodologies advocate for continuous integration and testing, where development and testing activities overlap and support each other throughout an iteration.

D is incorrect because agile methodologies encourage a wide range of testing types, including both functional and non-functional, as well as exploratory testing, to ensure a comprehensive quality assessment.