We prefer to develop system level tests while developing system level requirements. This approach offers a host of program wide benefits

• Simultaneous test development helps to assure that requirements are actually testable.
• The availability of a test description provides an additional perspective to help the implementer understand the requirement.
• The requirements team and testing team benefit from interaction early in the project.
• Test description development helps the requirements developers to provide more complete requirement coverage
• Test are described by developers with greatest understanding of the requirements, in a time frame when they are still fresh.