Budget Buddy - GitHub Copilot Demo Lab

Budget Buddy is a small Python budget tracker designed for Microsoft GH-300 demonstrations. It is intentionally a working but immature app: the happy path runs, starter tests pass, coverage is low, and realistic TODOs, bugs, security issues, and performance problems are left for GitHub Copilot to improve.

The goal is to show Copilot as more than autocomplete: codebase explanation, inline edits, agent mode, test generation, debugging, security review, refactoring, documentation, and PR-style summaries.

Current Demo State

• Runnable app: python main.py
• Starter tests: 8 tests
• Current coverage target: about 30%
• Workshop goal: use Copilot to reach 90%+ coverage
• Intentional issues: documented in INTENTIONAL_ISSUES.md
• Trainer flow: documented in DEMO_SCRIPT.md

Quick Start

.\setup_demo.ps1
.\.venv\Scripts\Activate.ps1
python main.py
pytest

If PowerShell blocks script execution, run:

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

What The App Does

Budget Buddy reads sample transactions from data/sample_transactions.csv, builds a simple monthly budget report, and logs:

• income
• expenses
• remaining budget
• net cash flow
• savings rate
• largest expense
• spending by category
• a paginated transaction table

Main Files

File	Purpose
main.py	Runnable demo app and report orchestration
calculator.py	Budget calculations with intentional edge-case bugs
data_processor.py	Transaction filtering, grouping, duplicate detection, and TODOs
file_handler.py	CSV/JSON file I/O with an intentional path traversal gap
data_table.py	Generic table helper used by the app
logger.py	Centralized logging utility
tests	Sparse starter tests for the coverage journey

Demo Flow (GH-300 modules)

The trainer flow in DEMO_SCRIPT.md is aligned to the five course modules:

1. Module 1 — Introduction: run setup_demo.ps1 and python main.py to frame the use case.
2. Module 2 — Exploring Features: Chat, Inline Chat, CLI, and prompts with context (security review of file handling).
3. Module 3 — Developer Use Cases: generate, transform, optimize, document, and a DevOps beat (Dockerfile + CI).
4. Module 4 — Building Unit Tests: the coverage journey from ~30% to 90%+.
5. Module 5 — Advanced Capabilities: Agent Mode, AGENT.md, Skills, MCP, and PR review/summary.

Useful Copilot Prompts

Reusable prompts live in .github/prompts:

• generate-tests.prompt.md
• security-review.prompt.md
• refactor-performance.prompt.md
• agent-feature.prompt.md
• devops-snippet.prompt.md
• pr-summary.prompt.md

Agent Customization Assets

Module 5 showcases how Copilot follows project-level guidance:

• AGENT.md — operating manual for agents in this repo.
• .github/copilot-instructions.md — repo-wide rules.
• .github/skills — task playbooks (SKILL.md), e.g. adding a budget report section.

Validation Commands

python main.py
pytest
pytest --cov=. --cov-report=term-missing

During the demo, after Copilot generates enough tests and fixes, change the coverage threshold in pytest.ini from 30 to 90 and rerun pytest.

Trainer Notes

This repository is intentionally not production-ready. Do not remove the TODOs and bugs from the starter state unless you also update INTENTIONAL_ISSUES.md and DEMO_SCRIPT.md.