Thanks very much for the reply.
There are a couple of features a gateway test may fit better for the purpose of our assessments over regular homework.
1. We can set a time limit to a gateway test so it can better simulate a test setting.
2. Students will not know whether what they have answered are correct or not until the end of the test (so trial-and-error is a less favourable option for the students especially for multiple-choice or matching problems).
3. Students get a final score only after they complete a test. We can then use these final scores to recommend study materials.
4. Gateway tests can display the entire test at once (rather than question by question without creating a pdf). This provides a more convenient way for students to look at all the questions and either decide which questions to start with or decide if they should study more before coming back to the tests at a later time.
These are some of the reasons we prefer gateway tests for our assessments. Regular homework will also be used but we prefer to incorporated them into study materials rather than assessments.