Fill-in-the-blank tests. These are only useful for the most basic kinds of knowledge and are nearly never useful above Certificate II level. They don't contribute to assessment of competence.
Written examinations that must be kept secret until they are given. These are not re-usable and you need to re-write them afresh every time you assess someone.
Multiple-choice tests. These are very difficult to write well, and writers should have extra studies in education. Modern multiple-choice tests are very sophisticated. They usually require very extensive trialing, so they it is usually only worthwile if they are used for large numbers of students. If not done well, they are plagued by validity problems; for example, you think you're testing comprehension or interpretion, but are actually only testing remembered information.