Utility for testing app logic

app-tester.js

/**
 * Utility for testing hyperapp app/state logic. Pass it an init parameter
 * and an effectHandler - a function that will replace every effecter used
 * it will be called with (originalEffecter, payload) every time an effect
 * is used allowing you to ovverride it and test that the right effecter
 * was called, et c. 
 * 
 * Returns an object with some useful functions: getState allows you to
 * inspect the state at any time, stop stops the app. dispatch dispatches
 * actions. 
 *
 * Subscriptions not supported yet. Nor views - but views are beyond
 * the scope/purpose of this. This is just for state-logic.
 *
 *
 * @template S
 * @param {import('hyperapp').Dispatchable<S>} init
 * @param {<X>(effecter: Effecter<S,X>, payload:X)=>void} effectHandler
 * @returns {{
 * 	getState: () => S,
 *  stop: () => void,
 * 	dispatch: import('hyperapp').Dispatch<S>
 * }}
 */
export const default (init, effectHandler = () => {}) => {
	/**@type {<X>(effecter: import('hyperapp').Effecter<S,X>) => import("hyperapp").Effecter<S,X>} */
	const getMockEffect = effecter => (dispatch, payload) => {
		effectHandler(effecter, payload)
	}

	/**@type {S} */
	let state
	const dispatch = app({
		init: init,
		dispatch: dispatch => (action, payload) => {
			if (Array.isArray(action)) {
				if (typeof action[0] !== "function") {
					state = action[0]
					//@ts-ignore
					action = [
						action[0],
						...action
							.slice(1)
							//@ts-ignore
							.map(f => (typeof f === "function" ? getMockEffect(f) : [getMockEffect(f[0]), f[1]])),
					]
				}
			} else if (typeof action !== "function") {
				state = /**@type {S}*/ (action)
			}
			dispatch(action, payload)
		},
	})
	const getState = () => state
	//@ts-ignore
	const stop = () => dispatch()
	return { getState, dispatch, stop }
}