Systemd/test/test-execute/exec-umask-0177.service

[Unit]
Description=Test for UMask

[Service]
ExecStart=/bin/sh -x -c 'rm /tmp/test-exec-umask; touch /tmp/test-exec-umask; mode=$$(stat -c %%a /tmp/test-exec-umask); test "$$mode" = "600"'
Type=oneshot
UMask=0177
PrivateTmp=yes