It depends what you want to say:
I will be there in a week. (A week from now is when I will go.)
I will be there for a week. (The duration of my visit.)
In the US, we say "On the weekend," not "at the weekend." We would also say "on weekdays" -- but I don't know what other dialects would say.
There is no good opposite to the adjective 'test' - perhaps 'actual.'
This is not a test scenario - it's an actual emergency!
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