Development Practices

# GitHub Flow — simple and effective for most teams

# 1. Create a feature branch from main
git checkout main
git pull origin main
git checkout -b feature/add-expense-categories

# 2. Make commits with clear messages
git commit -m "feat: add category dropdown to expense form"
git commit -m "test: add unit tests for category validation"
git commit -m "fix: prevent empty category submission"

# 3. Push and open PR
git push origin feature/add-expense-categories
# Open PR → get 2 reviews → merge → auto-deploy

# Conventional Commits format
# feat: new feature | fix: bug fix | docs: docs only
# refactor: code change | test: add tests | chore: build/deps

// Step 1: RED — Write failing test first
describe('BudgetCalculator', () => {
  it('warns when spending exceeds 80% of budget', () => {
    const calc = new BudgetCalculator({ limit: 1000 });
    calc.addExpense(850);
    expect(calc.isNearLimit()).toBe(true);
  });
});
// → Test fails: BudgetCalculator is not defined ❌

// Step 2: GREEN — Write minimum code to pass
class BudgetCalculator {
  constructor({ limit }) { this.limit = limit; this.spent = 0; }
  addExpense(amount) { this.spent += amount; }
  isNearLimit() { return (this.spent / this.limit) >= 0.8; }
}
// → Test passes ✅

// Step 3: REFACTOR — Improve without breaking tests
class BudgetCalculator {
  constructor({ limit, warningThreshold = 0.8 }) {
    this.limit = limit;
    this.warningThreshold = warningThreshold;
    this.spent = 0;
  }
  addExpense(amount) {
    if (amount <= 0) throw new Error('Amount must be positive');
    this.spent += amount;
  }
  get spentPercentage() { return this.spent / this.limit; }
  isNearLimit() { return this.spentPercentage >= this.warningThreshold; }
}
// → Still passes ✅ — now cleaner and more configurable