Initial commit: Create comprehensive Git playground

- Multi-language source code (Python, JavaScript, Java, C++, Go)
- Configuration files (JSON, YAML, INI)
- Sample data files (CSV, JSON, logs)
- Binary and media assets (PNG, SVG, PDF)
- Test files and deployment scripts
- Nested directory structure for testing Git features

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/test_calculator.js

@@ -0,0 +1,53 @@
+const Calculator = require('../../src/calculator');
+
+describe('Calculator', () => {
+    let calculator;
+
+    beforeEach(() => {
+        calculator = new Calculator();
+    });
+
+    test('should add two numbers correctly', () => {
+        expect(calculator.add(2, 3)).toBe(5);
+        expect(calculator.add(-1, 1)).toBe(0);
+        expect(calculator.add(0, 0)).toBe(0);
+    });
+
+    test('should subtract two numbers correctly', () => {
+        expect(calculator.subtract(5, 3)).toBe(2);
+        expect(calculator.subtract(1, 1)).toBe(0);
+        expect(calculator.subtract(0, 5)).toBe(-5);
+    });
+
+    test('should multiply two numbers correctly', () => {
+        expect(calculator.multiply(3, 4)).toBe(12);
+        expect(calculator.multiply(-2, 3)).toBe(-6);
+        expect(calculator.multiply(0, 5)).toBe(0);
+    });
+
+    test('should divide two numbers correctly', () => {
+        expect(calculator.divide(10, 2)).toBe(5);
+        expect(calculator.divide(7, 2)).toBe(3.5);
+        expect(calculator.divide(-6, 3)).toBe(-2);
+    });
+
+    test('should throw error when dividing by zero', () => {
+        expect(() => calculator.divide(5, 0)).toThrow('Division by zero is not allowed');
+    });
+
+    test('should maintain calculation history', () => {
+        calculator.add(2, 3);
+        calculator.multiply(4, 5);
+        
+        const history = calculator.getHistory();
+        expect(history).toHaveLength(2);
+        expect(history[0]).toBe('2 + 3 = 5');
+        expect(history[1]).toBe('4 * 5 = 20');
+    });
+
+    test('should clear history', () => {
+        calculator.add(1, 1);
+        calculator.clearHistory();
+        expect(calculator.getHistory()).toHaveLength(0);
+    });
+});