In v model requirement specification and run in parallel to acceptance testing and so on. See all steps that run parallel to each other below.

Requirement specification-------------------------------------------------------->Acceptance testing Function specification-------------------------------------------------------------->System testing Technical specification--------------------------------------------------------------->Integration testing Program specification----------------------------------------------------------------->Unit testing Coding------------------------------------------------------------------------------------->Unit testing

Req specification-Capturing user needs

Functional specification-Definition of Functional requirements to meet user needs

Technical Specifications-Technical design of functions defined in Functional specification. Matching the system requirements to computer modules and how those modules interact with each other.

Program Specification-Detailed design of each unit or module to be built.