The fact that your test will assess your ability to respond to questions targeting unseen texts and questions about a film that you watched in class means that an important step to take in preparation for your test is to familiarise yourself with a range of techniques, including those that you have learned in class, as well as other techniques which you believe would be useful to know and understand. The film will primarily contain visual techniques, which you must be familiar with, that is, understand their general effect and their significance in the film. You may also wish to remember a set of quotes from the film which you believe may be useful. Of course, whether you need to do this depends on the specifications of your test, which you know best. In terms of the unseen component, knowing and being able to interpret both literary and visual techniques will support your ability to analyse such texts, allowing you to provide good-quality responses. Whether you need to familiarise yourself with visual techniques for the unseen component depends on whether stimuli will be in written form only, in which case you would only need to maximise your knowledge of literary techniques.
If applicable, you should also ensure that you understand the main themes/ideas/issues of the film as this will support your ability to establish better connections between your points and the questions (for example, by discussing the optimal technique that highlights a particular theme), therefore strengthening your answers.
A method of preparation for the unseen component would be to analyse a range of relevant texts, which can come from books that you may have read or by performing a Google search. Doing so will allow you to determine instances of particular techniques being used within those texts, enabling you to identify relevant techniques in the actual exam faster. You can also take this a step further by creating your own questions targeting those texts, giving you the opportunity to apply your knowledge of the techniques and, in the case of written stimuli, linking them with relevant quotes from the texts.
I hope this helps!