Set variable inside if statement not working

Question

I have file1.txt and test.bat in the same folder.

Inside test.bat:

This works:

SET test=file1.txt
COPY %test% file2.txt

This does not work:

IF ""=="" (
SET test=file1.txt
COPY %test% file2.txt
)

Why? The only difference is "if" statement.

Whats more interesting:

IF ""=="" (
COPY file1.txt file2.txt
)

works

Answer 1

This works:

setlocal enabledelayedexpansion 

IF ""=="" (
SET test=file1.txt
COPY !test! file2.txt
)

More about "enabledelayedexpansion": https://ss64.com/nt/delayedexpansion.html