Systemd-analyze
Use the systemd-analyze verify command to check if a SystemD service file is valid and has no syntax errors.
sudo systemd-analyze verify /etc/systemd/system/my-service.service
If the service file is valid, the command will return nothing. If there are any errors, they will be displayed in the output.
/etc/systemd/system/my-service.service:3: Failed to add dependency on my-service.service, ignoring: Invalid argument