Bash not recognising strings as equal

I have two variables line and sorted, which are both space-delimited strings of numbers. Part of my script depends on checking whether these two strings are equal:

if [[ $sorted == $line ]]
then
echo "test"
fi

When running this I get no output. A visual check, using: echo $sorted and echo $line gives two seemingly similar outputs.

I thought that this may be due to either of the two outputs having an extra white space character at the end, so I decided to check whether removing spaces from the strings removed the problem:

test1=`echo $sorted | tr -d ' '`
test2=`echo $line | tr -d ' '`

Subsequently performing:

if [[ "$test1" == "$test2" ]]
then 
echo "test"
fi

Did give the desired "test" output. However, when comparing the number of characters of both variables using wc, the output is the same for both variables. Furthermore, checking the number of white space characters in line and sorted with echo <variable> | grep -o "\s" | wc -l also gives the same output for both variables.

My question is what could be causing this behaviour; running tr removes the problem, yet counting the number of white spaces with wc and grep shows that the number of spaces (or at least, characters) is similar.