test: unit tests for dns drift/sync + hap-bridge, vendored framework [#769]

Moved from KNEL/PFVCluster tests/unit with repo-relative paths.

https://projects.knownelement.com/issues/769#note-4152

tests/run-tests.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+# Minimal unit-test runner: executes tests/unit/*.sh, each self-asserting.
+set -uo pipefail
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+PASS=0; FAIL=0; FAILED=""
+for t in "$ROOT"/tests/unit/*.sh; do
+    [ -e "$t" ] || continue
+    if bash "$t" >"/tmp/rt-$(basename "$t").log" 2>&1; then
+        PASS=$((PASS+1)); echo "ok   $(basename "$t")"
+    else
+        FAIL=$((FAIL+1)); FAILED="$FAILED $(basename "$t")"; echo "FAIL $(basename "$t")"
+    fi
+done
+echo "passed=$PASS failed=$FAIL$FAILED"
+[ "$FAIL" -eq 0 ]