svelte/test/runtime/samples/custom-method/_config.js

export default {
	html: '<button>+1</button>\n\n<p>0</p>',
	test ( assert, component, target, window ) {
		const button = target.querySelector( 'button' );
		const event = new window.MouseEvent( 'click' );

		button.dispatchEvent( event );
		assert.equal( component.get().counter, 1 );
		assert.equal( target.innerHTML, '<button>+1</button>\n\n<p>1</p>' );

		button.dispatchEvent( event );
		assert.equal( component.get().counter, 2 );
		assert.equal( target.innerHTML, '<button>+1</button>\n\n<p>2</p>' );

		assert.equal( component.foo(), 42 );
	}
};