porcupine-md/jonggrang/debugging-systematically

# Write a failing test that reproduces the bug
it('reproduces bug #123', async () => {
  // The exact scenario that causes the bug
  const result = await service.doThing(buggyInput);
  expect(result).toBe(expectedValue); // This fails currently
});

Full system broken?
  → Is it the database connection or the business logic?
    → Is it in the controller or the service?
      → Is it in the query or the parsing?

// Add assertion to confirm hypothesis
console.assert(typeof userId === 'string', `userId is ${typeof userId}`);

// BUG: forgot await
const user = getUser(id); // returns Promise, not User
user.name; // undefined
// FIX:
const user = await getUser(id);

// BUG: assuming chain never null
const name = user.profile.address.city;
// FIX:
const name = user?.profile?.address?.city ?? 'Unknown';

// BUG: two async ops on same resource
await Promise.all([updateUser(id, {a: 1}), updateUser(id, {b: 2})]);
// One update overwrites the other
// FIX: serialize or use atomic DB operation
await db.user.update({ where: {id}, data: {a: 1, b: 2} });

# Node.js debugging
node --inspect src/index.js
# Then open chrome://inspect
 
# Print full error stack
process.on('unhandledRejection', (reason) => {
  console.error('Unhandled rejection:', reason);
});