This app constructs open cloze tests and vocabulary lists from Wikipedia articles. My students really like doing these tests and even ask for them! Something that is quite unusual in the classroom.
The reason why is because tests can be constructed in real time related to topics people find important. Checking understanding and finding alternative words just seems to happen naturally. Completing a test is also a way for students to demonstrate that they have actually understood a significant text in English. Confidence and motivation levels increase accordingly and are enhanced by having immediate feedback.