It varies depending on the manufacturer. The product may say that is a kit, but it lacks some material needed. Though, this case is less likely to happen. Most water test kits have a complete set of materials. It includes a variety of test strips, tubes, containers, a vial for the guide, and an instruction manual.
However, if you want to get the complete deal, you have to look for brands that are a lot more expensive than the usual. The more materials it has, the more expensive it is. It is not that expensive anyway. It is still affordable. But if you really want to get a complete package, look for the ones that have everything you need.