 Mae'r next type of test is called the diagnostic test and what a diagnostic test is really doing is telling us about the student's current strengths and weaknesses. A diagnostic test can also give us some indication of the student's aptitude and tell us something about whether or not they're going to be able to learn a particular type of material. One of the main things that a diagnostic test can do is that it will allow us to concentrate our planning by telling us what the students already know and the gaps in their knowledge. So a diagnostic test is very, very useful for the teacher in terms of the curriculum plan. The next type of test is called the progress test and it's one that whatever teaching situation you find yourself in, you're probably going to be involved in one way or another. Typically for progress tests, again, all four skills are tested. This type of test is often required by the school or the language centre that you're working in and even so by the parents to show that learning has taken place. The duration of time that the progress test is taken over can vary. It could be a particular unit test that's done when a unit is completed in a book. It could be a term test, it could be half-year or it could be an end of year. So there are different lengths of time over which these progress tests are covering. The progress test can be a very, very useful test for the teacher because quite often it will indicate from the whole class if there are any areas that they're struggling with and it tells us that we need to cover that particular area of the curriculum again. If we have a particular topic that all the students are getting incorrect and it tells us that that class weakness needs to be readdressed, we need to cover that particular area again.