test: add unit tests and Jest configuration

- Add basic test cases for BundleSizeAnalyzer
- Configure Jest with TypeScript support
- Add ts-jest and test dependencies
- Fix CI/CD test failures

__tests__/core.test.ts

@@ -0,0 +1,42 @@
+import { BundleSizeAnalyzer } from '../src/core/analyzer';
+
+describe('BundleSizeAnalyzer', () => {
+  it('should be defined', () => {
+    const analyzer = new BundleSizeAnalyzer({
+      maxSize: 500,
+      outputFormat: 'json',
+      outputPath: './reports'
+    });
+    expect(analyzer).toBeDefined();
+  });
+
+  it('should initialize with correct options', () => {
+    const options = {
+      maxSize: 500,
+      outputFormat: 'json' as const,
+      outputPath: './reports'
+    };
+    const analyzer = new BundleSizeAnalyzer(options);
+    expect(analyzer).toHaveProperty('options.maxSize', options.maxSize);
+    expect(analyzer).toHaveProperty('options.outputFormat', options.outputFormat);
+    expect(analyzer).toHaveProperty('options.outputPath', options.outputPath);
+  });
+
+  it('should have default compression enabled', () => {
+    const analyzer = new BundleSizeAnalyzer({
+      maxSize: 500,
+      outputFormat: 'json',
+      outputPath: './reports'
+    });
+    expect(analyzer).toHaveProperty('options.compression', true);
+  });
+
+  it('should have empty rules by default', () => {
+    const analyzer = new BundleSizeAnalyzer({
+      maxSize: 500,
+      outputFormat: 'json',
+      outputPath: './reports'
+    });
+    expect(analyzer).toHaveProperty('options.rules', []);
+  });
+});