not sure

src/game-loop/intro-title-agents.test.ts

@@ -0,0 +1,97 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { AGENT_FLOAT_COUNT } from '../pipelines/agents/agent-generation/agent';
+import { createIntroTitleAgents } from './intro-title-agents';
+
+const installCanvasMask = () => {
+  Object.defineProperty(globalThis, 'document', {
+    configurable: true,
+    value: {
+      createElement: vi.fn(() => {
+        const canvas = {
+          width: 0,
+          height: 0,
+          getContext: vi.fn(() => ({
+            clearRect: vi.fn(),
+            fillStyle: '',
+            fillText: vi.fn(),
+            font: '',
+            getImageData: vi.fn(() => {
+              const data = new Uint8ClampedArray(canvas.width * canvas.height * 4);
+              for (let i = 3; i < data.length; i += 4) {
+                data[i] = 255;
+              }
+              return { data };
+            }),
+            lineJoin: '',
+            lineWidth: 0,
+            measureText: vi.fn((text: string) => ({
+              actualBoundingBoxAscent: 10,
+              actualBoundingBoxDescent: 4,
+              width: text.length * 10,
+            })),
+            strokeStyle: '',
+            strokeText: vi.fn(),
+            textAlign: '',
+            textBaseline: '',
+          })),
+        };
+
+        return canvas;
+      }),
+    },
+  });
+};
+
+describe('createIntroTitleAgents', () => {
+  beforeEach(() => {
+    installCanvasMask();
+  });
+
+  afterEach(() => {
+    Reflect.deleteProperty(globalThis, 'document');
+  });
+
+  it('creates deterministic agents for the same seed and progress', () => {
+    const first = createIntroTitleAgents({
+      count: 4,
+      height: 32,
+      progress: 0.4,
+      seed: 123,
+      width: 64,
+    });
+    const second = createIntroTitleAgents({
+      count: 4,
+      height: 32,
+      progress: 0.4,
+      seed: 123,
+      width: 64,
+    });
+
+    expect(Array.from(first)).toEqual(Array.from(second));
+  });
+
+  it('preserves targets while advancing positions for a later intro progress', () => {
+    const initial = createIntroTitleAgents({
+      count: 1,
+      height: 32,
+      progress: 0,
+      seed: 456,
+      width: 64,
+    });
+    const later = createIntroTitleAgents({
+      count: 1,
+      height: 32,
+      progress: 0.8,
+      seed: 456,
+      width: 64,
+    });
+
+    expect(later[0]).not.toBe(initial[0]);
+    expect(later[1]).not.toBe(initial[1]);
+    expect(later[4]).toBe(initial[4]);
+    expect(later[5]).toBe(initial[5]);
+    expect(later[7]).toBe(initial[7]);
+    expect(later.length).toBe(AGENT_FLOAT_COUNT);
+  });
+});