test(engine): scripted full-game integration test

src/engine/integration.test.ts

@@ -0,0 +1,47 @@
+import { describe, it, expect } from 'vitest';
+import { DuplicateGame } from './game';
+import { playSymmetric } from './test-helpers';
+import { legalSyncedMoves } from './legality';
+import { ghosts } from './ghosts';
+import { evaluateStatus } from './endgame';
+import { serialize, deserialize } from './notation';
+
+describe('integration: a scripted game played to checkmate', () => {
+  it('plays Fool\'s mate, stays consistent throughout, and ends correctly', () => {
+    const g = new DuplicateGame();
+
+    // The game is live and ongoing until the mate.
+    expect(evaluateStatus(g).state).toBe('playing');
+    expect(legalSyncedMoves(g).length).toBeGreaterThan(0);
+
+    playSymmetric(g, [
+      [{ from: 'f2', to: 'f3' }, { from: 'e7', to: 'e5' }],
+      [{ from: 'g2', to: 'g4' }, { from: 'd8', to: 'h4' }],
+    ]);
+
+    // No captures occurred, so there are no ghosts.
+    expect(ghosts(g)).toEqual([]);
+
+    // North is checkmated.
+    const status = evaluateStatus(g);
+    expect(status.state).toBe('checkmate');
+    expect(status.result?.N).toBe('loss');
+    expect(legalSyncedMoves(g)).toEqual([]);
+
+    // The game round-trips through save/load and reproduces the same outcome.
+    const restored = new DuplicateGame(deserialize(serialize(g.history)));
+    expect(evaluateStatus(restored).state).toBe('checkmate');
+    expect(restored.history).toEqual(g.history);
+  });
+
+  it('undo from the mated position restores a playable game', () => {
+    const g = new DuplicateGame();
+    playSymmetric(g, [
+      [{ from: 'f2', to: 'f3' }, { from: 'e7', to: 'e5' }],
+      [{ from: 'g2', to: 'g4' }, { from: 'd8', to: 'h4' }],
+    ]);
+    g.undo(); // take back W's d8h4
+    expect(evaluateStatus(g).state).toBe('playing');
+    expect(g.currentPlayer).toBe('W');
+  });
+});