Systemd/test/test-execute/exec-environment.service

[Unit]
Description=Test for Environment

[Service]
ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6"'
Type=oneshot
Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"