diff --git a/test/test-functions b/test/test-functions
index 00a808bf28..a4b7efb5ec 100644
--- a/test/test-functions
+++ b/test/test-functions
@@ -778,9 +778,23 @@ if [[ ! -e "$ASAN_RT_PATH" ]]; then
     exit 1
 fi
 
+# Suppress certain leaks reported by LSan (either in external tools or bogus
+# ones)
+# Docs: # https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#suppressions
+#
+# - fsck is called by systemd-homed and is reporting a leak we're not interested
+#   in
+# - libLLVM is a "side effect" caused by the previous fsck leak
+cat >/systemd-lsan.supp <<INNER_EOF
+leak:/bin/fsck$
+leak:/sbin/fsck$
+leak:/lib/libLLVM
+INNER_EOF
+
+DEFAULT_LSAN_OPTIONS=${LSAN_OPTIONS:-}:suppressions=/systemd-lsan.supp
 DEFAULT_ASAN_OPTIONS=${ASAN_OPTIONS:-strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1}
 DEFAULT_UBSAN_OPTIONS=${UBSAN_OPTIONS:-print_stacktrace=1:print_summary=1:halt_on_error=1}
-DEFAULT_ENVIRONMENT="ASAN_OPTIONS=\$DEFAULT_ASAN_OPTIONS UBSAN_OPTIONS=\$DEFAULT_UBSAN_OPTIONS"
+DEFAULT_ENVIRONMENT="ASAN_OPTIONS=\$DEFAULT_ASAN_OPTIONS UBSAN_OPTIONS=\$DEFAULT_UBSAN_OPTIONS LSAN_OPTIONS=\$DEFAULT_LSAN_OPTIONS"
 
 # As right now bash is the PID 1, we can't expect PATH to have a sane value.
 # Let's make one to prevent unexpected "<bin> not found" issues in the future
@@ -2083,7 +2097,7 @@ dfatal() {
 
 
 # Generic substring function.  If $2 is in $1, return 0.
-strstr() { [ "${1#*$2*}" != "$1" ]; }
+strstr() { [ "${1#*"$2"*}" != "$1" ]; }
 
 # normalize_path <path>
 # Prints the normalized path, where it removes any duplicated
@@ -2498,12 +2512,12 @@ image_install() {
 install_kmod_with_fw() {
     local module="${1:?}"
     # no need to go further if the module is already installed
-    [[ -e "${initdir:?}/lib/modules/${KERNEL_VER:?}/${module##*/lib/modules/$KERNEL_VER/}" ]] && return 0
+    [[ -e "${initdir:?}/lib/modules/${KERNEL_VER:?}/${module##*"/lib/modules/$KERNEL_VER/"}" ]] && return 0
     [[ -e "$initdir/.kernelmodseen/${module##*/}" ]] && return 0
 
     [ -d "$initdir/.kernelmodseen" ] && : >"$initdir/.kernelmodseen/${module##*/}"
 
-    inst_simple "$module" "/lib/modules/$KERNEL_VER/${module##*/lib/modules/$KERNEL_VER/}" || return $?
+    inst_simple "$module" "/lib/modules/$KERNEL_VER/${module##*"/lib/modules/$KERNEL_VER/"}" || return $?
 
     local modname="${module##*/}"
     local fwdir found fw
diff --git a/test/units/testsuite-55.sh b/test/units/testsuite-55.sh
index b265c8cce7..db13964311 100755
--- a/test/units/testsuite-55.sh
+++ b/test/units/testsuite-55.sh
@@ -60,36 +60,29 @@ if ! systemctl status testsuite-55-testchill.service; then exit 24; fi
 
 # Make sure we also work correctly on user units.
 
-runas() {
-    declare userid=$1
-    shift
-    # shellcheck disable=SC2016
-    su "$userid" -s /bin/sh -c 'XDG_RUNTIME_DIR=/run/user/$UID exec "$@"' -- sh "$@"
-}
-
-runas testuser systemctl start --user testsuite-55-testchill.service
-runas testuser systemctl start --user testsuite-55-testbloat.service
+systemctl start --machine "testuser@.host" --user testsuite-55-testchill.service
+systemctl start --machine "testuser@.host" --user testsuite-55-testbloat.service
 
 # Verify systemd-oomd is monitoring the expected units
 oomctl | grep -E "/user.slice.*/testsuite-55-workload.slice"
 oomctl | grep "20.00%"
 oomctl | grep "Default Memory Pressure Duration: 2s"
 
-runas testuser systemctl --user status testsuite-55-testchill.service
+systemctl --machine "testuser@.host" --user status testsuite-55-testchill.service
 
 # systemd-oomd watches for elevated pressure for 2 seconds before acting.
 # It can take time to build up pressure so either wait 2 minutes or for the service to fail.
 timeout="$(date -ud "2 minutes" +%s)"
 while [[ $(date -u +%s) -le $timeout ]]; do
-    if ! runas testuser systemctl --user status testsuite-55-testbloat.service; then
+    if ! systemctl --machine "testuser@.host" --user status testsuite-55-testbloat.service; then
         break
     fi
     sleep 2
 done
 
 # testbloat should be killed and testchill should be fine
-if runas testuser systemctl --user status testsuite-55-testbloat.service; then exit 42; fi
-if ! runas testuser systemctl --user status testsuite-55-testchill.service; then exit 24; fi
+if systemctl --machine "testuser@.host" --user status testsuite-55-testbloat.service; then exit 42; fi
+if ! systemctl --machine "testuser@.host" --user status testsuite-55-testchill.service; then exit 24; fi
 
 # only run this portion of the test if we can set xattrs
 if setfattr -n user.xattr_test -v 1 /sys/fs/cgroup/; then