feat: Implement loading screen with retro 80s aesthetic and unit tests

tests/unit/loading.test.js

@@ -0,0 +1,46 @@
+/**
+ * Unit tests for LoadingScreen class
+ */
+
+const LoadingScreen = require('../../src/js/screens/loading');
+
+describe('LoadingScreen', () => {
+  let loadingScreen;
+
+  beforeEach(() => {
+    loadingScreen = new LoadingScreen();
+  });
+
+  describe('constructor', () => {
+    it('should initialize with progress 0', () => {
+      expect(loadingScreen.getProgress()).toBe(0);
+    });
+
+    it('should have assets array', () => {
+      expect(loadingScreen.assets).toBeDefined();
+      expect(Array.isArray(loadingScreen.assets)).toBe(true);
+      expect(loadingScreen.assets.length).toBeGreaterThan(0);
+    });
+  });
+
+  describe('getProgress', () => {
+    it('should return current progress', () => {
+      expect(loadingScreen.getProgress()).toBe(0);
+      
+      // Simulate progress update
+      loadingScreen.progress = 50;
+      expect(loadingScreen.getProgress()).toBe(50);
+    });
+  });
+
+  describe('asset loading', () => {
+    it('should have expected assets', () => {
+      expect(loadingScreen.assets).toContain('texture1.png');
+      expect(loadingScreen.assets).toContain('texture2.png');
+      expect(loadingScreen.assets).toContain('sound1.mp3');
+      expect(loadingScreen.assets).toContain('sound2.mp3');
+      expect(loadingScreen.assets).toContain('model1.obj');
+      expect(loadingScreen.assets).toContain('model2.obj');
+    });
+  });
+});