svelte/test/runtime/samples/transition-js-each-block-keyed-intro-outro/_config.js

export default {
	props: {
		things: [{ name: 'a' }, { name: 'b' }, { name: 'c' }]
	},

	intro: true,

	test({ assert, component, target, raf }) {
		const divs = target.querySelectorAll('div');
		divs[0].i = 0; // for debugging
		divs[1].i = 1;
		divs[2].i = 2;

		assert.equal(divs[0].foo, 0);
		assert.equal(divs[1].foo, 0);
		assert.equal(divs[2].foo, 0);

		raf.tick(100);
		assert.equal(divs[0].foo, 1);
		assert.equal(divs[1].foo, 1);
		assert.equal(divs[2].foo, 1);

		component.things = [{ name: 'a' }, { name: 'c' }];

		const divs2 = target.querySelectorAll('div');
		assert.strictEqual(divs[0], divs2[0]);
		assert.strictEqual(divs[1], divs2[1]);
		assert.strictEqual(divs[2], divs2[2]);

		raf.tick(150);
		assert.equal(divs[0].foo, 1);
		assert.equal(divs[1].foo, 0.5);
		assert.equal(divs[2].foo, 1);

		component.things = [{ name: 'a' }, { name: 'b' }, { name: 'c' }];

		raf.tick(175);
		assert.equal(divs[0].foo, 1);
		assert.equal(divs[1].foo, 0.75);
		assert.equal(divs[2].foo, 1);

		raf.tick(225);
		const divs3 = target.querySelectorAll('div');
		assert.strictEqual(divs[0], divs3[0]);
		assert.strictEqual(divs[1], divs3[1]);
		assert.strictEqual(divs[2], divs3[2]);

		assert.equal(divs[0].foo, 1);
		assert.equal(divs[1].foo, 1);
		assert.equal(divs[2].foo, 1);
	}
};