test-never-passing-assertion

an assertion written so that it can never pass — `expect.objectContaining` pairing a key with `undefined`

Deterministic checkblocking by defaultbasetests

The argument

Assertions That Can Never Pass

An assertion that no implementation can satisfy is found by a failed run, and whoever reads the red test has to prove by hand that the test, not the code, is wrong. Write each assertion in a form whose meaning matches how it reads.

expect.objectContaining never takes an undefined value. It reads as "the object has these values", so expect.objectContaining({ ticketRef: undefined }) reads as "and ticketRef is absent" — but the matcher first requires every key it names to be present. An object without the key never matches, and an object read back from disk never has it: JSON.stringify drops a key holding undefined. Say what you mean instead:
- the key is absent — drop it from the matcher and compare Object.hasOwn(value, 'ticketRef') against false;
- the value is undefined, whether or not the key exists — assert value.ticketRef with toBe(undefined).

// ❌ never passes against a record read from disk — the key is not there to compare
expect(readRecord({ cwd, name })).toEqual(expect.objectContaining({ name, ticketRef: undefined }));

// ✅ states absence in a form that can pass
const record = readRecord({ cwd, name });

expect({ name: record.name, carriesTicketRef: Object.hasOwn(record, 'ticketRef') }).toStrictEqual({ name, carriesTicketRef: false });

The proof

failsubject.unit.test.ts

import { expect, describe, test } from '@jest/globals';

describe('subject', () => {
	test('reads back a record written without a ticket', () => {
		const record = JSON.parse('{"name":"add-search-basics"}');

		expect(record).toEqual(expect.objectContaining({ name: 'add-search-basics', ticketRef: undefined }));
	});
});

passsubject.unit.test.ts

import { expect, describe, test } from '@jest/globals';

describe('subject', () => {
	test('reads back a record written without a ticket', () => {
		const record = JSON.parse('{"name":"add-search-basics"}');

		expect({ name: record.name, carriesTicketRef: Object.hasOwn(record, 'ticketRef') }).toStrictEqual({
			name: 'add-search-basics',
			carriesTicketRef: false,
		});
	});
});

Turn it down

Both lines go in your lightsout.config.json.

"standards-checks": { "test-never-passing-assertion": "advisory" }

"standards-checks": { "test-never-passing-assertion": "off" }