Native English speakers only, how to say "you must test if the computer works"?

Yeah that sounds right

1. Before the repairman leaves, test the computer to see if it is working properly.

examine

As a native English Speaker, I wouldn't say that at all.

I would reword it to:-

1. Before the repairman leaves, you should test the computer for fault, or faults!

'Must' is incorrect here, because that would suggest a life or death situation. It isn't!

"test to see if the computer works"

or

"test whether the computer works"

Most people would probably say "check to see that the computer works".

Wrong.

It should be “whether”.

Test can be followed by a whether clause.

Why do you think that "test" "cannot be followed by a whether clause"? Where the hell did you get that idiotic idea?

I would say:

Before the repairman leaves, you must test that the computer works.

or

Before the repairman leaves, test that the computer works.

You don't need a comma.

To be honest you should not have to test the computer that is the repairman's job (Lol)

Normally (informally) you would say

- Before the repairman leaves you must test to see if the computer works.

or

- Before the repairman leaves you must test and see if the computer works.

More formally you might say

- Before the repairman leaves you should test the computer to make sure it works.

or (better)

- Before the repairman leaves you should test the computer to make sure it is functioning correctly.