JSTOR Research Basics Course Modules
Note: If you are looking specifically at plagiarism, use Module 3.
Other Plagiarism Exercises
There is also a good set of exercises from Cornell University, that allows guests to go through the samples to determine if there is plagiarism. This is the link: https://plagiarism.arts.cornell.edu/tutorial/exercises.cfm
This site from Indiana University has several different levels of plagiarism, from what might be common in high school through graduate school. Users can take tests at each level (Novice through Expert) to get a certificate. https://academy.sitehost.iu.edu/index.html