How to fix echo printing literal \n (backslash newline)

Problem:

You want to echo into a file like this:

echo "\ntest\n" > test.txt

but after doing that, test.txt contains the literal

\ntest\n

Solution:

Use echo -e (-e means: interpret backslash escapes):

echo -e "\ntest\n" > test.txt

After doing that, test.txt will contain test with a newline before and after.