Test case for initctl signal

This commit implements a test for the signal feature of initctl. The
existing service used in tests (`common/service.sh`) has been extended
with a signal trap handler. When SIGUSR1 is received, it will write the
string `'USR1'` to `/tmp/usr1.log`. The test will run `initctl signal
service.sh SIGUSR1` and assert that the contents of the file
`/tmp/usr1.log` really is `USR1`.

test/signal-service.sh

@@ -0,0 +1,36 @@
+#!/bin/sh
+# Verifies initctl can send arbitrary signals (USR1 in this case) to finit managed services
+
+set -eu
+
+TEST_DIR=$(dirname "$0")
+
+# shellcheck source=/dev/null
+. "$TEST_DIR/tenv/lib.sh"
+
+test_teardown() {
+    say "Test done $(date)"
+    say "Running test teardown."
+
+    texec rm -f "$FINIT_CONF"
+    texec rm -f /test_assets/service.sh
+}
+
+say "Test start $(date)"
+
+cp "$TEST_DIR"/common/service.sh "$TENV_ROOT"/test_assets/
+
+say 'Ensure file system is cleared'
+texec rm -f /tmp/usr1.log
+
+say "Add service stanza in $FINIT_CONF"
+texec sh -c "echo 'service [2345] kill:20 log /test_assets/service.sh -- Test service' > $FINIT_CONF"
+
+say 'Reload Finit'
+texec sh -c "initctl reload"
+
+say 'Send SIGUSR1 to service...'
+texec sh -c "initctl signal service.sh SIGUSR1"
+
+# shellcheck disable=SC2016
+retry 'assert "service.sh received SIGUSR" "$(texec cat /tmp/usr1.log)" = "USR1"' 10 1