The Systematic Test and Evaluation Process (STEP) model, developed by William C. Hetzel, fundamentally integrates testing activities into the software development lifecycle from the very beginning. A core principle of STEP is that testing and development are parallel, not sequential, activities. Therefore, as requirements and use cases are being defined and specified, corresponding test cases are designed to validate them. This early design of tests ensures that requirements are testable, clear, and complete, effectively using the testing process to prevent defects from being introduced into later stages.

B. Defect prevention is a primary goal of the STEP model, not a secondary one. By validating requirements and design early, STEP aims to find and fix errors before they become code defects.

C. The STEP model explicitly requires that the requirements specification and test design processes overlap. Test design begins during the requirements phase to provide early feedback and validation.

D. This describes a traditional waterfall approach. In the STEP model, testware design begins in parallel with the requirements and system design phases, long before coding is completed.

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1. Hetzel, W. C. (1988). The Complete Guide to Software Testing (2nd ed.). QED Information Sciences. In Chapter 3, "A System for Testing," Hetzel introduces the STEP model, stating, "Test development is carried out in parallel with software development... Test requirements are defined when the software requirements are defined." (p. 38). Figure 3.2 on p. 39 explicitly shows "Test Design" occurring in parallel with "System Requirements."

2. Burnstein, I. (2003). Practical Software Testing: A Process-Oriented Approach. Springer-Verlag. In Chapter 2, "A Software Quality Program," the text discusses lifecycle models that integrate testing. It describes models like STEP as promoting "a set of testing activities that are planned and managed and that are integrated into the software life cycle." This integration starts at the requirements phase to support verification and validation activities (Section 2.3.2).

3. Utting, M., & Legeard, B. (2007). Practical Model-Based Testing: A Tools Approach. Morgan Kaufmann. The book discusses the evolution of testing processes, referencing early lifecycle integration models. It notes that models like STEP were developed to overcome the waterfall limitation of late-stage testing by initiating test design and planning "as soon as the requirements are being specified" (Chapter 1, Section 1.3.2).