diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
new file mode 100644
index 0000000..311c2b9
--- /dev/null
+++ b/.github/workflows/unit-tests.yml
@@ -0,0 +1,19 @@
+# Copyright 2026 Hewlett Packard Enterprise Development LP
+---
+name: unit-tests
+
+'on':
+  pull_request:
+
+jobs:
+  jenkins-library-guard-unit-test:
+    name: Jenkins @Library guard unit test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          fetch-depth: 0
+
+      - name: Run Jenkins @Library guard unit test
+        run: ./tests/guard-jenkins-library-pin-test.sh
diff --git a/checks/guard-jenkins-library-pin.sh b/checks/guard-jenkins-library-pin.sh
index 2f54ed7..e79167e 100755
--- a/checks/guard-jenkins-library-pin.sh
+++ b/checks/guard-jenkins-library-pin.sh
@@ -58,7 +58,7 @@ if [[ ${#JENKINS_FILES[@]} -eq 0 ]]; then
   exit 0
 fi
 
-library_regex='@Library[[:space:]]*\('
+library_regex='@Library[[:space:]]*[(]'
 
 guard_failed=0
 for rel_path in "${JENKINS_FILES[@]}"; do
diff --git a/tests/guard-jenkins-library-pin-test.sh b/tests/guard-jenkins-library-pin-test.sh
new file mode 100755
index 0000000..1db3a54
--- /dev/null
+++ b/tests/guard-jenkins-library-pin-test.sh
@@ -0,0 +1,233 @@
+#!/usr/bin/env bash
+# Copyright 2026 Hewlett Packard Enterprise Development LP
+set -euo pipefail
+
+# Unit tests for checks/guard-jenkins-library-pin.sh
+#
+# Each case builds a minimal temporary git repository with a fixture
+# Jenkinsfile, runs the guard, and verifies:
+#   - expected exit code
+#   - expected stdout/stderr content
+#
+# Usage: ./tests/guard-jenkins-library-pin-test.sh
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+GUARD="${REPO_ROOT}/checks/guard-jenkins-library-pin.sh"
+
+pass_count=0
+fail_count=0
+
+WORK_DIR=""
+cleanup_all() {
+  if [[ -n "${WORK_DIR}" ]]; then
+    # Some git-created paths can be non-writable (files and/or dirs,
+    # platform-dependent); make the tree writable so recursive cleanup is
+    # reliable across environments.
+    chmod -R u+w "${WORK_DIR}" 2>/dev/null || true
+    rm -rf "${WORK_DIR}" 2>/dev/null || true
+  fi
+}
+trap cleanup_all EXIT
+
+WORK_DIR="$(mktemp -d)"
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+pass() { echo "[PASS] $1"; pass_count=$(( pass_count + 1 )); }
+fail() { echo "[FAIL] $1" >&2; fail_count=$(( fail_count + 1 )); }
+
+# make_repo DIR
+# Initialize a throwaway git repo with a committed state ready for ls-files.
+make_repo() {
+  local dir="$1"
+  mkdir -p "${dir}"
+  git -C "${dir}" init -q
+  git -C "${dir}" config user.email "test@test.local"
+  git -C "${dir}" config user.name "Test"
+}
+
+# commit_file REPO_DIR REL_PATH
+# Stage and commit the file at REL_PATH inside REPO_DIR.
+commit_file() {
+  local dir="$1"
+  local rel="$2"
+  git -C "${dir}" add "${rel}"
+  git -C "${dir}" commit -qm "test fixture: ${rel}"
+}
+
+# run_case NAME WORKDIR EXPECTED_EXIT [STDOUT_SUBSTR] [STDERR_SUBSTR]
+# Runs the guard and reports pass/fail.
+run_case() {
+  local name="$1"
+  local workdir="$2"
+  local expected_exit="$3"
+  local stdout_substr="${4:-}"
+  local stderr_substr="${5:-}"
+
+  local out_file="${WORK_DIR}/${name}.out"
+  local err_file="${WORK_DIR}/${name}.err"
+  local actual_exit=0
+
+  "${GUARD}" --target-root "${workdir}" \
+    >"${out_file}" 2>"${err_file}" || actual_exit=$?
+
+  local ok=1
+
+  # --- exit code check ---
+  if [[ "${actual_exit}" -ne "${expected_exit}" ]]; then
+    echo "  [${name}] expected exit ${expected_exit}, got ${actual_exit}" >&2
+    echo "  stdout: $(cat "${out_file}")" >&2
+    echo "  stderr: $(cat "${err_file}")" >&2
+    ok=0
+  fi
+
+  # --- stdout content check ---
+  if [[ -n "${stdout_substr}" ]] && \
+       ! grep -qF "${stdout_substr}" "${out_file}"; then
+    echo "  [${name}] stdout missing: ${stdout_substr}" >&2
+    echo "  stdout was: $(cat "${out_file}")" >&2
+    ok=0
+  fi
+
+  # --- stderr content check ---
+  if [[ -n "${stderr_substr}" ]] && \
+       ! grep -qF "${stderr_substr}" "${err_file}"; then
+    echo "  [${name}] stderr missing: ${stderr_substr}" >&2
+    echo "  stderr was: $(cat "${err_file}")" >&2
+    ok=0
+  fi
+
+  if [[ "${ok}" -eq 1 ]]; then
+    pass "${name}"
+  else
+    fail "${name}"
+  fi
+}
+
+# ---------------------------------------------------------------------------
+# Case 1 — no Jenkinsfile in repo: guard exits 0, reports no candidates
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_no_jenkinsfile"
+  make_repo "${d}"
+  touch "${d}/README.md"
+  commit_file "${d}" README.md
+
+  run_case \
+    "no_jenkinsfile" "${d}" 0 \
+    "no Jenkinsfile candidates found"
+}
+
+# ---------------------------------------------------------------------------
+# Case 2 — Jenkinsfile with no @Library: guard exits 0, reports ok
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_clean"
+  make_repo "${d}"
+  cat > "${d}/Jenkinsfile" <<'GROOVY'
+// clean fixture: no active @Library reference
+GROOVY
+  commit_file "${d}" Jenkinsfile
+
+  run_case \
+    "clean_jenkinsfile" "${d}" 0 \
+    "no active @Library references found"
+}
+
+# ---------------------------------------------------------------------------
+# Case 3 — active @Library reference: guard exits 1, reports blocked
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_active_library"
+  make_repo "${d}"
+  cat > "${d}/Jenkinsfile" <<'GROOVY'
+@Library("my-shared-lib") _
+GROOVY
+  commit_file "${d}" Jenkinsfile
+
+  run_case \
+    "active_library_blocked" "${d}" 1 \
+    "" \
+    "blocked: active @Library reference"
+}
+
+# ---------------------------------------------------------------------------
+# Case 4 — @Library in a // line comment: must be ignored, guard exits 0
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_line_comment"
+  make_repo "${d}"
+  cat > "${d}/Jenkinsfile" <<'GROOVY'
+// @Library("my-shared-lib") _
+GROOVY
+  commit_file "${d}" Jenkinsfile
+
+  run_case \
+    "library_in_line_comment_ignored" "${d}" 0 \
+    "no active @Library references found"
+}
+
+# ---------------------------------------------------------------------------
+# Case 5 — @Library inside a /* */ block comment: must be ignored, exits 0
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_block_comment"
+  make_repo "${d}"
+  cat > "${d}/Jenkinsfile" <<'GROOVY'
+/*
+ * Example usage: @Library("my-shared-lib") _
+ */
+GROOVY
+  commit_file "${d}" Jenkinsfile
+
+  run_case \
+    "library_in_block_comment_ignored" "${d}" 0 \
+    "no active @Library references found"
+}
+
+# ---------------------------------------------------------------------------
+# Case 6 — @Library with whitespace before paren (spacing variant): blocked
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_spaced_paren"
+  make_repo "${d}"
+  cat > "${d}/Jenkinsfile" <<'GROOVY'
+@Library  ("my-shared-lib") _
+GROOVY
+  commit_file "${d}" Jenkinsfile
+
+  run_case \
+    "library_spaced_paren_blocked" "${d}" 1 \
+    "" \
+    "blocked: active @Library reference"
+}
+
+# ---------------------------------------------------------------------------
+# Case 7 — Jenkinsfile in a subdirectory: guard must detect it
+# ---------------------------------------------------------------------------
+{
+  d="${WORK_DIR}/case_subdir"
+  make_repo "${d}"
+  mkdir -p "${d}/jobs"
+  cat > "${d}/jobs/Jenkinsfile" <<'GROOVY'
+@Library("my-shared-lib") _
+GROOVY
+  commit_file "${d}" jobs/Jenkinsfile
+
+  run_case \
+    "active_library_in_subdir_blocked" "${d}" 1 \
+    "" \
+    "blocked: active @Library reference"
+}
+
+# ---------------------------------------------------------------------------
+# Summary
+# ---------------------------------------------------------------------------
+echo ""
+echo "Results: ${pass_count} passed, ${fail_count} failed"
+
+if [[ "${fail_count}" -ne 0 ]]; then
+  exit 1
+fi