diff --git a/Makefile b/Makefile
index 0b7bb631c4..740af90629 100644
--- a/Makefile
+++ b/Makefile
@@ -24,6 +24,7 @@ test:
 	@# Filter out integration.
 	$(GO) list ./... | grep -vw integration | xargs $(GO_TEST)
 	cd cmd && $(GO_TEST) ./...
+	sh deploy/healthcheck_test.sh
 
 test-with-libpfm: GO_FLAGS=-race -tags libpfm
 test-with-libpfm: test
diff --git a/deploy/healthcheck.sh b/deploy/healthcheck.sh
index df65e493fc..2c57871cd9 100644
--- a/deploy/healthcheck.sh
+++ b/deploy/healthcheck.sh
@@ -18,11 +18,20 @@
 PORT=8080
 
 # Extract port from the cadvisor process command line
-if [ -f /proc/1/cmdline ]; then
-    CMDLINE=$(tr '\0' ' ' < /proc/1/cmdline)
+# Allow tests to supply a fake cmdline file.
+CMDLINE_FILE="${CADVISOR_HEALTHCHECK_CMDLINE_FILE:-/proc/1/cmdline}"
+if [ -f "${CMDLINE_FILE}" ]; then
+    CMDLINE=$(tr '\0' ' ' < "${CMDLINE_FILE}")
 
-    # Look for -port=XXXX or --port=XXXX
+    # Look for -port=XXXX, --port=XXXX, -port XXXX, or --port XXXX.
+    next_arg_is_port=false
     for arg in $CMDLINE; do
+        if [ "${next_arg_is_port}" = true ]; then
+            PORT="${arg}"
+            next_arg_is_port=false
+            continue
+        fi
+
         case "$arg" in
             -port=*)
                 PORT="${arg#-port=}"
@@ -30,6 +39,9 @@ if [ -f /proc/1/cmdline ]; then
             --port=*)
                 PORT="${arg#--port=}"
                 ;;
+            -port|--port)
+                next_arg_is_port=true
+                ;;
         esac
     done
 fi
diff --git a/deploy/healthcheck_test.sh b/deploy/healthcheck_test.sh
new file mode 100644
index 0000000000..bad2a84094
--- /dev/null
+++ b/deploy/healthcheck_test.sh
@@ -0,0 +1,56 @@
+#!/bin/sh
+
+# Copyright 2026 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -eu
+
+SCRIPT_DIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+
+TMPDIR=$(mktemp -d)
+trap 'rm -rf "${TMPDIR}"' EXIT
+
+run_case() {
+  name="$1"
+  expected_port="$2"
+  shift 2
+
+  cmdline_file="${TMPDIR}/${name}.cmdline"
+  wget_log="${TMPDIR}/${name}.wget"
+
+  : > "${cmdline_file}"
+  for arg in "$@"; do
+    printf '%s\0' "${arg}" >> "${cmdline_file}"
+  done
+
+  cat > "${TMPDIR}/wget" <<EOF
+#!/bin/sh
+printf '%s\n' "\$*" > "${wget_log}"
+case "\$*" in
+  *"http://localhost:${expected_port}/healthz"*) exit 0 ;;
+  *) exit 1 ;;
+esac
+EOF
+  chmod +x "${TMPDIR}/wget"
+
+  PATH="${TMPDIR}:${PATH}" \
+    CADVISOR_HEALTHCHECK_CMDLINE_FILE="${cmdline_file}" \
+    sh "${SCRIPT_DIR}/healthcheck.sh"
+}
+
+run_case default 8080 cadvisor
+run_case single_dash_equals 9090 cadvisor -port=9090
+run_case double_dash_equals 9091 cadvisor --port=9091
+run_case single_dash_space 9092 cadvisor -port 9092
+run_case double_dash_space 9093 cadvisor --port 9093