bash: xargs passing variable

Question

How can a global script variable be passed to the command of xargs? I tried it this way:

TEST=hallo2
echo "hallo" | xargs sh -c 'echo passed=$1 test=$TEST' sh

Output:

passed=hallo test=

I know I could use the {} token but I need to do it this way!

I'm using bash.

Answer 1

Added as an answer as@chepner suggested.

export the variable TEST:

export TEST=hallo2
echo "hallo" | xargs sh -c 'echo passed=$1 test="$TEST"' sh

Answer 2

Take variable $TEST out from the quotes:

 TEST=hallo2
 echo "hallo" | xargs sh -c 'echo passed=$1 test='$TEST sh