Do you refer to the actual project or the requirements document when writing the test case?

The test case is written as an integral and important part of the testing process, but are we writing the use case according to the actual project or the requirement document as the standard?

In a company of a certain size, the test case design is completed and before the test is started, there must be a work, that is, the test case review. The project Director, project developers, product personnel, and all of the project's stakeholders, such as visual interaction, are seated together, initiated by the testers, to conduct a review of the test case, and the best time to review is when the project has been started and part of the coding is done, when the tester writes to the requirements document On the basis of the test case, the project team members further check the details of the project requirements, if there is inconsistency in understanding the place, can be discussed immediately, agreed. Because at this time the project is still in development, if the point of disagreement in the function has not been developed naturally is the best, even if the function has been developed, at this time the cost of modification is significantly lower than the completion of the development, so the requirements of the standard test cases for the design and grooming is the need to re-filter, The review process is a clean-up of the point of demand disputes, which can greatly improve the accuracy of requirements and reduce unnecessary development costs.

Do you refer to the actual project or the requirements document when writing the test case?