After a test is completed it should show up in a student's list of homework sets and tests (albeit at the bottom of the list). The "set" name will be the name of the test with ",vN" appended (for version N, where N is 1 for the first test and so on). A student should be able to view the test using that list and select "show correct answers" and check the test as s/he can for a regular homework set.
In addition, s/he should be able to select "show correct answers" after grading the test, and then click "check test" to see them.
Gavin