Do not create hoaxes
Please do not attempt to put misinformation into Wikipedia to test our ability to detect and remove it. This has been done before, with varying results. Most hoaxes are marked for deletion within a few hours of being created. However, some very sophisticated hoaxes, such as articles about made-up historical individuals with detailed biographical information and fake references, have lasted for several years before being detected. These hoax articles hurt the reputation of Wikipedia as an encyclopedia.
It has been tried, tested, and confirmed: it is indeed possible to insert hoaxes into Wikipedia, just as it is possible to insert profanity (it's an uncensored encyclopedia, after all). This is an inevitable consequence of being a free encyclopedia that anyone can edit. A hoax is simply a more obscure, less obvious form of vandalism, and perpetrators of hoaxes are subject to blocking and banning.
Misinformation on Wikipedia misleads readers, causing them to make errors with real consequences, including hurt feelings, public embarrassment, reprints of books, lost points on school assignments, and other costs. Some hoaxes about living people may be defamatory, which could expose Wikipedia to legal consequences (see Wikipedia:Biographies of living persons). With some articles, like medical topics, they could lead to injury or death. Additionally, maintaining and improving hoax articles requires resources that volunteers could be dedicating to useful topics. Although it is important to read Wikipedia critically and to try to improve the reliability of its content, it is best to do this directly, by correcting false information, rather than by "testing" the system by creating a hoax article or content to see if Wikipedia will detect the hoax.
If you are interested in how accurate Wikipedia is, a more constructive test method is to try to find inaccurate statements that are already in Wikipedia, and then to check to see how long they have been in place and, if possible, correct them.