svelte/test/runtime/samples/dev-warning-destroy-twice/_config.js

export default {
	dev: true,

	test(assert, component) {
		const warn = console.warn; // eslint-disable-line no-console

		const warnings = [];
		console.warn = warning => { // eslint-disable-line no-console
			warnings.push(warning);
		};

		component.destroy();
		component.destroy();

		assert.deepEqual(warnings, [
			`Component was already destroyed`
		]);

		console.warn = warn; // eslint-disable-line no-console
	}
};