Session tests only pass when the whole file runs

Problem Description

We added a hotfix pipeline that runs a single test by name before deploying: node --test --test-name-pattern='<name>'. Two tests in test/session.test.js fail immediately under it - one with TypeError: Cannot read properties of null (reading 'displayName') and one with Error: no active session. The same two tests are green in the normal full-file run, and have been for months.

We also moved the sign-out test up a couple of slots while debugging something unrelated, and two other tests went red in the full run as well. Moving it back made them green again. Nobody changed src/session.js in either direction.

The hotfix pipeline is not going away, and we want to be able to add tests anywhere in the file without auditing what runs before them.

Output Specification

1. Fix test/session.test.js so that every test passes both in a full node --test run and when it is the only test selected by --test-name-pattern, in any position in the file.
2. Keep all five tests and their assertions about what each scenario should produce. Do not modify src/session.js.
3. Write session-notes.md: why two tests fail alone and pass in the full run, why moving one unrelated test changed which tests were red, and the rule that keeps a newly added test from re-creating this.

Run node --test before you finish; it must pass.

Input Files

Extract the following files before beginning.

=============== FILE: package.json =============== { "name": "console-api", "version": "1.8.2", "private": true, "scripts": { "test": "node --test" } }

=============== FILE: src/session.js =============== 'use strict';

const USERS = { ada: { user: 'ada', displayName: 'Ada L.', role: 'admin' }, grace: { user: 'grace', displayName: 'Grace H.', role: 'auditor' }, };

let active = null;

function signIn(user) { const record = USERS[user]; if (!record) { throw new Error(unknown user: ${user}); } active = { ...record }; return active; }

function activeSession() { return active; }

function signOut() { active = null; }

function permissions() { if (!active) { throw new Error('no active session'); } return active.role === 'admin' ? ['read', 'write', 'admin'] : ['read']; }

module.exports = { signIn, activeSession, signOut, permissions };

=============== FILE: test/session.test.js =============== 'use strict';

const test = require('node:test'); const assert = require('node:assert/strict'); const { signIn, activeSession, signOut, permissions, } = require('../src/session');

test('signing in makes a session active', () => { const session = signIn('ada'); assert.equal(session.user, 'ada'); assert.equal(activeSession().user, 'ada'); });

test('the active session carries the display name', () => { assert.equal(activeSession().displayName, 'Ada L.'); });

test('an admin session can write', () => { assert.deepEqual(permissions(), ['read', 'write', 'admin']); });

test('signing out clears the active session', () => { signOut(); assert.equal(activeSession(), null); });

test('an auditor session is read only', () => { signIn('grace'); assert.deepEqual(permissions(), ['read']); });