Depending on the course and the need (a lot of my courses use enough "weird" words and Latin I don't have to worry about spell check!) I have used two different formats.
1. Either a drop-down list with random common misspellings of the word or a multiple choice with the same misspellings.
2. Audio files, annoying to set up but if I'm not too worried about spell check I record the audio and have them type the word they hear
The other thing I'm careful to do is set a (reasonable) time limit to the test to try and make it harder for them to reply on spellcheck, etc