const { observable } = require('../lib/index.js');

describe('observable', () => {
	it('returns its initialized value', () => {
		const a = observable(true);
		expect(a()).toEqual(true);
	});

	it('returns its set value', () => {
		const a = observable();
		expect(a()).toEqual(undefined);
		expect(a(true)).toEqual(true);
	});

	it('returns notifies dependents of updates', () => {
		let runCount = 0;
		let currentValue = 1;
		const a = observable();
		a.subscribe(val => {
			runCount += 1;
			expect(val).toEqual(currentValue);
		});
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(1);
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(1);
		currentValue = 2;
		expect(a(2)).toEqual(2);
		expect(runCount).toEqual(2);
		expect(a(2)).toEqual(2);
		expect(runCount).toEqual(2);
		currentValue = 1;
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(3);
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(3);
	});

	it('honors cancelled subscriptions', () => {
		let runCount = 0;
		let currentValue = 1;
		const a = observable();
		const cancelSubscription = a.subscribe(val => {
			runCount += 1;
			expect(val).toEqual(currentValue);
		});
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(1);
		expect(a(1)).toEqual(1);
		expect(runCount).toEqual(1);
		cancelSubscription();
		expect(a(3)).toEqual(3);
		expect(runCount).toEqual(1);
	});
});