diff --git a/src/Combat.characterization.test.js b/src/Combat.characterization.test.js
new file mode 100644
index 0000000..20ba7de
--- /dev/null
+++ b/src/Combat.characterization.test.js
@@ -0,0 +1,137 @@
+// Combat characterization. Lock updateDoc/setDoc patch for combat controls.
+
+import React from 'react';
+import { screen, fireEvent, waitFor } from '@testing-library/react';
+import '@testing-library/jest-dom';
+import { getCalls } from './__mocks__/firebase/_mock-db';
+import { setupReady, addMonsterViaUI, startCombatViaUI } from './testHelpers';
+
+function findCallsEnc() {
+  return getCalls().filter(c => c.fn === 'updateDoc' && c.path.includes('/encounters/'));
+}
+function lastEncCall() {
+  const calls = findCallsEnc();
+  return calls[calls.length - 1];
+}
+function findCallActiveDisplay(fn) {
+  return getCalls().filter(c => c.fn === fn && c.path.includes('activeDisplay/status'));
+}
+
+async function setupWithMonsters(names = ['A', 'B', 'C']) {
+  await setupReady('CombatCamp', 'CombatEnc');
+  for (const n of names) {
+    await addMonsterViaUI(n, 20, Number(n.charCodeAt(0) % 10));
+  }
+}
+
+describe('Combat -> Firebase', () => {
+  test('startEncounter: updateDoc sets isStarted/round/turn/current', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    const call = lastEncCall();
+    expect(call.data).toMatchObject({
+      isStarted: true,
+      isPaused: false,
+      round: 1,
+    });
+    expect(call.data.currentTurnParticipantId).toBeTruthy();
+    expect(call.data.turnOrderIds).toHaveLength(3);
+  });
+
+  test('startEncounter: also sets activeDisplay to this encounter', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    const adCalls = findCallActiveDisplay('setDoc');
+    const last = adCalls[adCalls.length - 1];
+    expect(last.data.activeCampaignId).toBeTruthy();
+    expect(last.data.activeEncounterId).toBeTruthy();
+  });
+
+  test('nextTurn: advances currentTurnParticipantId', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    const beforeId = lastEncCall().data.currentTurnParticipantId;
+
+    fireEvent.click(screen.getByRole('button', { name: /Next Turn/i }));
+    await waitFor(() => lastEncCall()?.data?.currentTurnParticipantId !== beforeId);
+    expect(lastEncCall().data.currentTurnParticipantId).not.toBe(beforeId);
+  });
+
+  test('nextTurn wrapping to round 1->2 increments round', async () => {
+    await setupWithMonsters(['A', 'B']);
+    await startCombatViaUI();
+
+    // advance through all participants to wrap
+    fireEvent.click(screen.getByRole('button', { name: /Next Turn/i })); // A->B (or 2nd)
+    await waitFor(() => lastEncCall()?.data?.currentTurnParticipantId);
+    fireEvent.click(screen.getByRole('button', { name: /Next Turn/i })); // wrap
+    await waitFor(() => lastEncCall()?.data?.round === 2);
+    expect(lastEncCall().data.round).toBe(2);
+  });
+
+  test('pause: updateDoc sets isPaused true', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    fireEvent.click(screen.getByRole('button', { name: /Pause Combat/i }));
+    await waitFor(() => lastEncCall()?.data?.isPaused === true);
+    expect(lastEncCall().data.isPaused).toBe(true);
+  });
+
+  test('resume: updateDoc sets isPaused false + recomputes turnOrder', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    fireEvent.click(screen.getByRole('button', { name: /Pause Combat/i }));
+    await waitFor(() => lastEncCall()?.data?.isPaused === true);
+    fireEvent.click(screen.getByRole('button', { name: /Resume Combat/i }));
+    await waitFor(() => lastEncCall()?.data?.isPaused === false);
+    const call = lastEncCall();
+    expect(call.data.isPaused).toBe(false);
+    expect(call.data.turnOrderIds).toHaveLength(3);
+  });
+
+  test('endEncounter: updateDoc resets all combat state', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    fireEvent.click(screen.getByRole('button', { name: /End Combat/i }));
+    fireEvent.click(await screen.findByRole('button', { name: /Confirm/i }));
+    await waitFor(() => lastEncCall()?.data?.isStarted === false);
+    const call = lastEncCall();
+    expect(call.data).toMatchObject({
+      isStarted: false,
+      isPaused: false,
+      round: 0,
+      currentTurnParticipantId: null,
+      turnOrderIds: [],
+    });
+  });
+
+  test('endEncounter: clears activeDisplay', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    fireEvent.click(screen.getByRole('button', { name: /End Combat/i }));
+    fireEvent.click(await screen.findByRole('button', { name: /Confirm/i }));
+    await waitFor(() => {
+      const adCalls = findCallActiveDisplay('setDoc');
+      const last = adCalls[adCalls.length - 1];
+      return last && last.data.activeCampaignId === null;
+    });
+    const adCalls = findCallActiveDisplay('setDoc');
+    const last = adCalls[adCalls.length - 1];
+    expect(last.data).toMatchObject({ activeCampaignId: null, activeEncounterId: null });
+  });
+
+  test('toggleHidePlayerHp: setDoc merge on activeDisplay/status', async () => {
+    await setupWithMonsters();
+    await startCombatViaUI();
+    const switchBtn = screen.getByRole('switch');
+    fireEvent.click(switchBtn);
+    await waitFor(() => {
+      const adCalls = findCallActiveDisplay('setDoc');
+      const last = adCalls[adCalls.length - 1];
+      return last && 'hidePlayerHp' in last.data;
+    });
+    const adCalls = findCallActiveDisplay('setDoc');
+    const last = adCalls[adCalls.length - 1];
+    expect(last.data).toHaveProperty('hidePlayerHp');
+  });
+});