You must have one in your possession by the time you start work.
Your contract is created in duplicate: one for you and one for your employer, Randstad. This kind of student contract is always for a limited period and ends on the expiry date.
You are also required to get a copy of the work regulations, for which you will sign a proof of receipt.
At Randstad it is possible to sign your employment contracts electronically. You can read how to do that here
am I first required to work for a trial period?
Maybe, but it must be stated in your contract.
Working as a temping student? Then you will generally receive your contracts for a 1-week period. In the case of temping, the trial period is generally 3 days. During this trial period either party is entitled to cancel the employment contract without notice or compensation.
Do you have a contract for a specific period? Then the trial period related to student employment is a minimum of 7 and maximum of 14 days. Moreover, neither you nor your employer are entitled to terminate the employment contract during the first 7 days. As from the 8th to the 14th day you or your employer may terminate the contract without notice or compensation.