write-tests

name	write-tests
description	Write tests the house way for this repo. Use when the user asks for tests, coverage, or verification of app logic or the habits data.

Write tests

House style

• Runner: node --test (built-in node:test), zero dependencies. Do not add jest/vitest/mocha.
• Location: tests/*.test.js, ES modules.
• Import real modules (app/habits.js); never copy fixtures of real data into the test.
• One describe per subject, assert from node:assert/strict.
• Test invariants and behavior, not implementation: "10 habits per pack", not "array index 3 equals X".
• DOM code in app.js is verified by hand in the browser — don't bolt on a DOM emulator for it.

Steps

1. Look at tests/habits.test.js for the existing pattern.
2. Add the smallest set of asserts that would fail if the logic broke.
3. Run node --test and show the output.