Implement calculator module using agentic workflow with isolated functions

DEVELOP_SUMMARY.md

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+# Development Phase Summary - Calculator Implementation
+
+## Overview
+Successfully implemented a simple calculator module with four basic arithmetic operations as requested.
+
+## Files Created
+
+### 1. Core Implementation: `src/calculator.js`
+- **Functions**: `add()`, `subtract()`, `multiply()`, `divide()`
+- **Exports**: Both named exports and default export (calculator object)
+- **Features**:
+  - Type validation on all inputs (throws TypeError if not numbers)
+  - Division by zero protection (throws Error)
+  - Comprehensive JSDoc documentation
+  - ES6 module syntax
+
+### 2. Test Suite: `tests/calculator.test.js`
+- **Test Count**: 18 comprehensive tests
+- **Coverage**:
+  - All four basic operations (addition, subtraction, multiplication, division)
+  - Edge cases: negative numbers, decimals, zero
+  - Error handling: type validation, division by zero (including negative zero)
+  - Calculator object methods
+- **Status**: ✅ All 18 tests passing
+- **Test Runner**: Custom lightweight test runner (no external dependencies)
+
+### 3. Configuration: `package.json`
+- Set up as ES6 module (`"type": "module"`)
+- Test script: `npm test`
+- No external dependencies
+
+### 4. Examples: `examples.js`
+- Demonstrates all calculator features
+- Shows basic operations, decimals, negative numbers
+- Includes error handling examples
+- Verified working output
+
+### 5. Documentation: `src/README.md`
+- Complete API reference for all functions
+- Usage examples
+- Error handling documentation
+- Implementation details
+
+## Testing Results
+
+```
+Tests passed: 18
+Tests failed: 0
+Exit code: 0
+```
+
+All tests verified and passing:
+- ✅ Basic arithmetic operations
+- ✅ Negative numbers
+- ✅ Decimal/floating-point numbers (with proper tolerance)
+- ✅ Type validation
+- ✅ Division by zero protection
+- ✅ Edge cases (zero, negative zero)
+
+## Code Quality
+
+### Code Review
+- ✅ Passed automated code review
+- ✅ Addressed all feedback items:
+  - Fixed floating-point comparison tolerance
+  - Simplified division by zero check
+  - Improved test robustness
+
+### Security Check (CodeQL)
+- ✅ Zero security vulnerabilities detected
+- ✅ No code quality issues
+- ✅ Clean security scan
+
+## Key Implementation Decisions
+
+1. **ES6 Modules**: Modern JavaScript standard, tree-shakeable
+2. **Type Safety**: Strict type checking on all operations
+3. **Error Handling**: Descriptive error messages with appropriate error types
+4. **Documentation**: JSDoc format for IDE intellisense support
+5. **No Dependencies**: Pure JavaScript implementation
+6. **Dual Export**: Named exports + default export for flexibility
+
+## Edge Cases Handled
+
+1. **Division by Zero**: Throws descriptive Error
+2. **Negative Zero**: Properly handled (JavaScript treats -0 === 0)
+3. **Floating Point**: Uses appropriate tolerance (1e-10) for comparisons
+4. **Type Validation**: Rejects non-numeric inputs with TypeError
+5. **Negative Numbers**: Full support for all operations
+6. **Decimal Numbers**: Proper handling with awareness of JS precision
+
+## Git Commits
+
+1. `22d9c58` - Initial implementation with all features
+2. `93db60e` - Code review improvements (division by zero, floating-point)
+3. `4e650fa` - Refinements (simplified zero check, better tolerance)
+
+## Handoff to Test Agent
+
+### What to Test
+
+The test-agent should focus on:
+
+1. **Extended Test Coverage**:
+   - Boundary values (Infinity, -Infinity, Number.MAX_VALUE, Number.MIN_VALUE)
+   - NaN handling (currently not validated)
+   - Very large numbers
+   - Very small numbers (close to zero)
+   - Chain operations
+
+2. **Performance Testing**:
+   - Operation speed
+   - Memory usage for many operations
+
+3. **Integration Testing**:
+   - Using calculator in different contexts
+   - Module import/export in various scenarios
+
+4. **Additional Edge Cases**:
+   - What happens with very long decimal chains?
+   - Precision loss scenarios
+   - Scientific notation numbers
+
+### Current Limitations
+
+Known areas that could be expanded:
+- No NaN validation (should we reject NaN inputs?)
+- No Infinity handling (currently allowed)
+- Floating-point precision issues are inherent to JavaScript
+- No operation history/memory
+- No support for chaining operations
+
+### Test Commands
+
+```bash
+# Run existing tests
+npm test
+
+# Run examples
+node examples.js
+
+# Verify calculator import
+node -e "import('./src/calculator.js').then(c => console.log(c.default.add(2,3)))"
+```
+
+### Files for Test Agent to Review
+
+- `/home/runner/work/agentic-workflow-blog/agentic-workflow-blog/src/calculator.js`
+- `/home/runner/work/agentic-workflow-blog/agentic-workflow-blog/tests/calculator.test.js`
+- `/home/runner/work/agentic-workflow-blog/agentic-workflow-blog/package.json`
+- `/home/runner/work/agentic-workflow-blog/agentic-workflow-blog/examples.js`
+- `/home/runner/work/agentic-workflow-blog/agentic-workflow-blog/src/README.md`
+
+## Summary
+
+✅ **Implementation Complete**: All four basic operations working correctly
+✅ **Tests Passing**: 18/18 tests successful
+✅ **Code Review**: Passed with improvements applied
+✅ **Security Scan**: Zero vulnerabilities
+✅ **Documentation**: Complete with examples and API reference
+✅ **Ready for Testing**: Handoff to test-agent for comprehensive validation
+
+The calculator is functional, well-tested, and ready for the next phase of the workflow.