It's not so easy to make a wish in English as you might think. In fact the grammar of wishing is quite complicated! For example, you can say both I wish to have an appointment .. and I want to have an appointment .. , but although you can say I want an appointment .., you cannot say I wish an appointment .. . Similarly, you can say I wish it would snow tomorrow, but you cannot say I wish you would pass your driving test tomorrow. You can say I wish she would give up smoking, but you cannot say I wish I would give up smoking. You can say I wish it was Saturday, but not I wish it was raining on Saturday or I wish it would rain on Saturday. You can say I wish it was raining today but not I wish it was raining yesterday. And so on.
What should you say instead of I wish you would pass your driving test?
What should you say instead of I wish I would stop smoking?
What should it be instead of I wish it was raining on Saturday?
Is there a difference between these two sentences, and if so, what is it?
I wish you wouldn't smoke so much.
I wish you didn't smoke so much.
Can you say I wish I would speak German? If not, what should you say?
Can you say I wish she would speak German. If so, what does it mean?
Instead of I wish you would pass your driving test, you should say I hope you pass your driving test!
Instead of saying I wish I would stop smoking, you should say I wish I could stop smoking.
I wish it was raining on Saturday is not possible and could be corrected in two ways, depending on the meaning: I wish it had rained on Saturday (i.e. it didn't rain last Saturday, but I wish it had) or I hope it rains on Saturday (i.e. I want it to rain this coming Saturday.)
There is a subtle difference between the sentences I wish you wouldn't smoke so much and
I wish you didn't smoke so much. The first one implies that I am asking you to stop; the second one expresses my unhappiness at the fact you smoke so much and my feeling that I probably can't do much about it.
You cannot say I wish I would speak German. It has to be I wish I could speak German.
You can say I wish she would speak German and if you do, you are implying that she can speak German but you are unhappy that she is not speaking it on this occasion. (For example, you have an arrangement with your German wife that she will always speak German with your children, but now she is speaking English to them and you don't like this!)
I haven't attempted in this short article to explain why some sentences are possible and others not etc. My intention has been to show that this is a complicated aspect of English for the non-native speaker. If you want to find out more, I suggest you read Practical English
Usage by M. Swan, Oxford University Press.