As the Contract works proceed towards completion the Contractor must demonstrate to the Employer that they comply with the requirements of the Contract, subject to relatively minor items of defective and outstanding work. In the Yellow and Silver books, in both editions, clause 12 sets out provisions relating to testing after completion. In the Yellow and Silver Books the tests must be carried out in accordance with: the test programme; and the notice given by the Contractor during the trial operation period, when the works or section are operating under stable conditions, that they are ready for any other tests on completion, including any performance tests. Taking over occurs when the works or sections have passed the tests on completion and are otherwise ready to be taken into commercial use and occupation by the Employer, subject to snagging or relatively minor items of defects or incomplete work.