diff --git a/src/integration.test.js b/src/integration.test.js
new file mode 100644
index 0000000..ea3190d
--- /dev/null
+++ b/src/integration.test.js
@@ -0,0 +1,106 @@
+import { beforeAll, describe, expect, test } from "bun:test";
+import { initCards } from "./cards.js";
+import { getEnemy, initEnemies } from "./enemies.js";
+import {
+  campfireRest,
+  campfireSmith,
+  createRunState,
+  endCombat,
+  pickReward,
+  revealRewards,
+  skipRewards,
+} from "./run.js";
+import { createCombatFromRun } from "./state.js";
+
+beforeAll(async () => {
+  await Promise.all([initCards(), initEnemies()]);
+});
+
+describe("skip all rewards → deck stays at 10", () => {
+  test("3 combats with skipped rewards leave deck unchanged", () => {
+    let run = createRunState("ironclad");
+    expect(run.deck).toHaveLength(10);
+
+    for (let i = 0; i < 3; i++) {
+      const { revealed, run: afterReveal } = revealRewards(run);
+      run = skipRewards(afterReveal, revealed);
+      expect(run.deck).toHaveLength(10);
+    }
+  });
+});
+
+describe("take every reward → deck grows", () => {
+  test("3 combats with picked rewards add 3 cards to deck", () => {
+    let run = createRunState("ironclad");
+    expect(run.deck).toHaveLength(10);
+
+    for (let i = 0; i < 3; i++) {
+      const { revealed, run: afterReveal } = revealRewards(run);
+      run = pickReward(afterReveal, revealed, 0);
+    }
+
+    expect(run.deck).toHaveLength(13);
+  });
+});
+
+describe("rest at campfires → HP carries into combat", () => {
+  test("healed HP is reflected in combat player state", () => {
+    let run = { ...createRunState("ironclad"), hp: 5 };
+    run = campfireRest(run);
+    expect(run.hp).toBe(8);
+
+    const combat = createCombatFromRun(run, "jaw_worm");
+    expect(combat.players[0].hp).toBe(8);
+  });
+
+  test("campfireRest caps at maxHp and combat reflects the cap", () => {
+    let run = { ...createRunState("ironclad"), hp: 10 };
+    run = campfireRest(run);
+    expect(run.hp).toBe(11);
+
+    const combat = createCombatFromRun(run, "jaw_worm");
+    expect(combat.players[0].hp).toBe(11);
+  });
+});
+
+describe("smith upgrades change cards in combat", () => {
+  test("smithed card appears in draw pile when combat is created", () => {
+    let run = createRunState("ironclad");
+    run = campfireSmith(run, "strike_r");
+    expect(run.deck).toContain("strike_r+");
+
+    const combat = createCombatFromRun(run, "jaw_worm");
+    const drawPile = combat.players[0].drawPile;
+    expect(drawPile).toContain("strike_r+");
+  });
+});
+
+describe("fresh run after death resets everything", () => {
+  test("death leaves hp 0, new run restores full HP and original deck", () => {
+    let run = createRunState("ironclad");
+
+    // simulate dying: endCombat with 0 HP
+    // ironclad gets +1 from burning blood, so post-combat hp is 1
+    run = endCombat(run, 0);
+    expect(run.hp).toBe(1);
+
+    // fresh run represents starting over
+    const fresh = createRunState("ironclad");
+    expect(fresh.hp).toBe(11);
+    expect(fresh.maxHp).toBe(11);
+    expect(fresh.deck).toHaveLength(10);
+    expect(fresh.combatCount).toBe(0);
+  });
+});
+
+describe("boss enemies are harder than encounter enemies", () => {
+  test("all bosses have higher HP than all encounter enemies", () => {
+    const bosses = ["slime_boss", "the_guardian"].map((id) => getEnemy(id));
+    const encounters = ["jaw_worm", "cultist"].map((id) => getEnemy(id));
+
+    const minBossHp = Math.min(...bosses.map((e) => e.hp));
+    const maxEncounterHp = Math.max(...encounters.map((e) => e.hp));
+
+    expect(minBossHp).toBeGreaterThan(maxEncounterHp);
+  });
+});