diff --git a/package.json b/package.json
index 1314403..b6bb3bb 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "Node.js CLI/library for V2H devices over ECHONET Lite",
   "main": "index.js",
   "scripts": {
-    "test": "node --check index.js && node --check cli.js",
+    "test": "node --check index.js && node --check cli.js && node --test",
     "lint": "node --check index.js && node --check cli.js && node --check lib/common.js && node --check lib/discover.js && node --check lib/status.js && node --check lib/format.js",
     "typecheck": "node --check index.js && node --check cli.js && node --check lib/common.js && node --check lib/discover.js && node --check lib/status.js && node --check lib/format.js && node --check scripts/safety-checks.js",
     "build": "npm pack --dry-run",
diff --git a/test/characterization.test.js b/test/characterization.test.js
new file mode 100644
index 0000000..97b5f05
--- /dev/null
+++ b/test/characterization.test.js
@@ -0,0 +1,185 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const { extractV2hObjectIds } = require('../lib/discover');
+const { buildStatus } = require('../lib/status');
+const { formatDiscoveredDevices, formatStatus } = require('../lib/format');
+
+const ANSI_RE = /\x1b\[[0-9;]*m/g;
+
+function stripAnsi(value) {
+  return String(value).replace(ANSI_RE, '');
+}
+
+function normalizeDynamicTableValues(value) {
+  return String(value)
+    .replace(/\b(?:\d{1,3}\.){3}\d{1,3}\b/g, '<IP>')
+    .replace(/\b[0-9a-fA-F]{6}\b/g, '<OBJECT_ID>');
+}
+
+test('extractV2hObjectIds: returns only 027e object ids from d5/d6 style payload', () => {
+  // Fixture-only instance-list payload (not network discovery output).
+  const payload = '03027e010ef001027e02';
+  assert.deepEqual(extractV2hObjectIds(payload), ['027e01', '027e02']);
+});
+
+test('extractV2hObjectIds: returns empty array for invalid payload', () => {
+  assert.deepEqual(extractV2hObjectIds(null), []);
+  assert.deepEqual(extractV2hObjectIds(''), []);
+  assert.deepEqual(extractV2hObjectIds('01027e'), []);
+});
+
+test('buildStatus: maps raw values into stable status fields/table', () => {
+  // Fixture-only values to characterize pure mapping behavior.
+  const status = buildStatus({
+    ip: '192.0.2.10',
+    objectId: '027e01',
+    raw: {
+      '80': '30',
+      '82': '1234',
+      '88': '41',
+      c2: '000001f4',
+      c4: '00000032',
+      c5: '00000fa0',
+      c6: '00000bb8',
+      c7: 'ff',
+      cc: '23',
+      ce: '000003e8',
+      cf: '0000012c',
+      da: '42',
+      e2: '00000258',
+      e4: '64',
+      e6: 'abcd1234',
+    },
+  });
+
+  assert.equal(status.connectionStatus, 'CONNECTED');
+  assert.equal(status.isVehicleConnected, true);
+  assert.equal(status.mode, 'CHARGE');
+  assert.equal(status.socPct, 100);
+
+  assert.deepEqual(status.table, {
+    'システム電源': 'ON',
+    '異常発生状態': '異常',
+    '充電器タイプ': 'DCタイプA(充放電)',
+    '定格充電能力(W)': 4000,
+    '定格放電能力(W)': 3000,
+    '車両接続・充放電可否状態': 'ff',
+    '車載電池の充電可能容量値(Wh)': 1000,
+    '車載電池の充電可能残容量(Wh)': 300,
+    '運転モード設定': '充電',
+    '車載電池の放電可能残容量(Wh)': 500,
+    '車載電池の放電可能残容量(%)': 50,
+    '車両ID': 'abcd1234',
+    '車載電池の残容量(Wh)': 600,
+    '車載電池の残容量(％)': 100,
+    '規格Version情報': '1234',
+  });
+});
+
+test('buildStatus: disconnected case keeps 車両ID as ff', () => {
+  const status = buildStatus({ ip: '192.0.2.11', objectId: '027e01', raw: { c7: '20' } });
+  assert.equal(status.connectionStatus, 'DISCONNECTED');
+  assert.equal(status.table['車両ID'], 'ff');
+});
+
+test('buildStatus: fallback handling for missing/unknown values', () => {
+  const status = buildStatus({ ip: '192.0.2.12', objectId: '027e99', raw: {} });
+  assert.equal(status.connectionStatus, 'UNKNOWN');
+  assert.equal(status.mode, 'UNKNOWN');
+  assert.equal(status.socPct, null);
+  assert.equal(status.table['システム電源'], 'OFF');
+  assert.equal(status.table['運転モード設定'], '取得できず');
+  assert.equal(status.table['充電器タイプ'], '取得できず');
+  assert.equal(status.table['規格Version情報'], null);
+});
+
+test('formatDiscoveredDevices: stable table output', () => {
+  const output = stripAnsi(formatDiscoveredDevices([
+    { ip: '192.0.2.10', objectId: '027e01' },
+    { ip: '192.0.2.11', objectId: '027e02' },
+  ]));
+  const normalized = normalizeDynamicTableValues(output);
+
+  assert.match(normalized, /IP address/);
+  assert.match(normalized, /Object ID/);
+  const rows = normalized
+    .split('\n')
+    .map((line) => line.trim())
+    .filter((line) => line.startsWith('<IP>'));
+
+  assert.equal(rows.length, 2);
+  rows.forEach((line) => {
+    const cols = line.split(/\s+/).filter(Boolean);
+    assert.equal(cols.length, 2);
+    assert.equal(cols[0], '<IP>');
+    assert.equal(cols[1], '<OBJECT_ID>');
+  });
+});
+
+test('formatDiscoveredDevices: keeps stable column order (fixture-only)', () => {
+  const output = stripAnsi(formatDiscoveredDevices([
+    { ip: '198.51.100.1', objectId: '0ef001' },
+  ]));
+  const normalized = normalizeDynamicTableValues(output);
+  const lines = normalized.split('\n').map((line) => line.trim()).filter(Boolean);
+
+  assert.match(lines[0], /^IP address\s+Object ID$/);
+});
+
+test('formatStatus: stable table output for known values', () => {
+  const status = {
+    table: {
+      'システム電源': 'ON',
+      '異常発生状態': '平常',
+      '充電器タイプ': 'DCタイプA(充放電)',
+      '定格充電能力(W)': 4000,
+      '定格放電能力(W)': 3000,
+      '車両接続・充放電可否状態': 'ff',
+      '車載電池の充電可能容量値(Wh)': 1000,
+      '車載電池の充電可能残容量(Wh)': 300,
+      '運転モード設定': '充電',
+      '車載電池の放電可能残容量(Wh)': 500,
+      '車載電池の放電可能残容量(%)': 50,
+      '車両ID': 'abcd1234',
+      '車載電池の残容量(Wh)': 600,
+      '車載電池の残容量(％)': 100,
+      '規格Version情報': '1234',
+    },
+  };
+
+  const output = stripAnsi(formatStatus(status));
+  assert.match(output, /項目名/);
+  assert.match(output, /システム電源/);
+  assert.match(output, /ON/);
+  assert.match(output, /平常/);
+  assert.match(output, /規格Version情報/);
+  assert.match(output, /1234/);
+});
+
+test('formatStatus: keeps stable label order (fixture-only)', () => {
+  const output = stripAnsi(formatStatus({ table: {} }));
+  const lines = output.split('\n').map((line) => line.trim()).filter(Boolean);
+  const headerIndex = lines.findIndex((line) => line.includes('項目名') && line.includes('値'));
+  assert.notEqual(headerIndex, -1);
+
+  const dataLines = lines.slice(headerIndex + 2); // skip header and delimiter
+  const labels = dataLines.map((line) => line.split(/\s+/)[0]);
+  assert.deepEqual(labels, [
+    'システム電源',
+    'ステータス',
+    '充電器タイプ',
+    '定格充電能力(W)',
+    '定格放電能力(W)',
+    '車両接続・充放電可否状態',
+    '車載電池の充電可能容量値(Wh)',
+    '車載電池の充電可能残容量(Wh)',
+    '運転モード設定',
+    '車載電池の放電可能残容量(Wh)',
+    '車載電池の放電可能残容量(%)',
+    '車両ID',
+    '車載電池の残容量(Wh)',
+    '車載電池の残容量(％)',
+    '規格Version情報',
+  ]);
+});