The Tento di Cruciamentum
More often than not the Slayer does not reach her 18th birthday. When this does happens, certain things are expected of both the Watcher and the Slayer by the Watcher's Council. The Cruciamentum is a test for both parties, dating back 1200 years.
Though this is not as long as the Slayer has been around, it is nearly so. The test is this: the Slayer must exhibit the ability to think fast, show courage, and defeat a vampire in a controlled environment without her Slayer strength, agility, or speed. The vampire has generally been starved, chained up, and is often a particularly vicious vampire making the Slayer's task especially dangerous. Escape is not an option as the Council sees to it that the Slayer and Vampire are locked into the environment until one is defeated. This information is kept from the Slayer leading up to the test, whom has no idea what is happening to her powers. The Slayer will often feel sick during that time, maybe coming down with a cold, which is does strike them as odd considering that Slayers don't get sick. The duties required of the Watcher are to in the week or so before the test, to hypnotize their charge (sometimes using crystals) and administer 3 injections that render the slayer temporarily powerless. They may also give the injections to the Slayer under false pretenses of the Slayer saying she feels ill or strange and the Watcher offers "medicine" of some kind. The effects do wear off, but for the time being leave the Slayer with the strength of a normal girl their size. The Watcher also has to keep this information from her at all costs. If she informs her of the upcoming test, the test is invalidated and called off. They will almost certainly lose their job as a result of this action.
If the Slayer is killed in her weakened state before the test is conducted, the Watcher in charge can ask to be reassigned to another location and/or job. Often, a Watcher will beg that his charge not be subjected this the test and is relieved of his/her duties and reassigned. This test and deception on the Watcher's part often creates a rift between Watcher and Slayer, and often creates tension between the Slayer and the Council as well.
Some Slayers who have faced Cruciamentum:
Millicent Rose Gresham in 1911 (passed)
Dorothy Singer in 1919 (passed)
Zoe Kuryakin in 1952 (killed before test)
Beryl Mackenzie in 1969 (passed)
Nikki Wood in 1973 (passed)
Peri Bohr in 1983 (passed)
Buffy Summers in 1999 (passed)