In my company, the customer needs, business requirements, and test plan are all housed within one document, called the DIOVV (Design Input, Output, Verification, Validation). the customer needs are listed as user needs in this document, which the product development then translates into design outputs (business requirements) with acceptance criteria that must be met via verification testing. The test plan is covered by the verification and validation sections. Verification testing is performed to ensure that all design outputs meet the specified design inputs, while design validation is performed by the final user evaluating the device to ensure it meets all the user needs.