Fail Early - Fail Often (FEFO). Prototype as often as possible - even in this phase - if some uncertainties exist that would prevent culmination of this phase. (See The Business and Hidden Values of Prototyping During Product Development ). 'Early-found' errors, deficiencies, misjudgments and 'ah-has!' allow quick mitigation when things are most in your control and investment is lowest. Also, there is no downside with customers or financial stakeholders. You also get a better product… faster.

Following are examples of requirements and documents:

• Tools & Equipment required for design and testing - software and hardware (PRS)
• Test Equipment calibration details (PRS)
• Tool calibration documents (EXR)
• Processes for designing and testing (SOP)
• Selection & control plans for Off-The-Shelf components (HW & SW) (SOP) - COTS or MOTS
• Prototype, Beta-test, clinical test plans (PRS), (SOP)
• Refine COM and COGS (DDOC, MRD - change control is in effect for the MRD)
• Commercial and industry-required test processes (EXR)
• Develop beta-tests and user trails (clinical trials for FDA products) (SOP) - done in close cooperation with marketing
• Functional Specification (PRS) and/or (DDOC)
• Refine the Theory Of Operations (DDOC)
• Most Likely ID concept (PRS) and/or (DDOC)
• User & other equipment Interfaces (PRS) and/or (DDOC)
• Mechanical Configuration (PRS) and/or (DDOC)
• Electrical Configuration (PRS) and/or (DDOC)
• Power budgets and requirements (DDOC) and/or (PRS)
• Software/firmware Configuration (PRS) and/or (DDOC)
• Appropriate design tools may be acquired in this stage.
• Architecture 'design review' and fault analysis (PRS, DTR2)
• Environmental robustness tests: drop, 'shake-rattle-and-roll, altitude, humidity, handling, etc.: see What Every Product Development Manager and Executive Need to Know about Product Testing for Unexpected Wear & Tear (PRS)