systemd/test/test-execute/exec-supplementarygroups-multiple-groups-withuid.service

[Unit]
Description=Test for Supplementary Group with multiple groups and Uid=1

[Service]
ExecStart=/bin/sh -x -c 'HAVE=0; for g in $$(id -G); do test "$$g" = "1" && HAVE=1; done; test "$$HAVE" -eq 1'
ExecStart=/bin/sh -x -c 'HAVE=0; for g in $$(id -G); do test "$$g" = "2" && HAVE=1; done; test "$$HAVE" -eq 1'
ExecStart=/bin/sh -x -c 'HAVE=0; for g in $$(id -G); do test "$$g" = "3" && HAVE=1; done; test "$$HAVE" -eq 1'
Type=oneshot
User=1
SupplementaryGroups=1 2 3