webpack/test/helpers/PluginEnvironment.js

module.exports = function PluginEnvironment() {
	const events = [];

	function addEvent(name, handler) {
		events.push({
			name,
			handler
		});
	}

	function getEventName(hookName) {
		// Convert a hook name to an event name.
		// e.g. `buildModule` -> `build-module`
		return hookName.replace(/[A-Z]/g, c => "-" + c.toLowerCase());
	}

	this.getEnvironmentStub = function() {
		const hooks = new Map();
		return {
			plugin: addEvent,
			// TODO: Figure out a better way of doing this
			// In the meanwhile, `hooks` is a `Proxy` which creates fake hooks
			// on demand. Instead of creating a dummy object with a few `Hook`
			// method, a custom `Hook` class could be used.
			hooks: new Proxy({}, {
				get(target, hookName) {
					let hook = hooks.get(hookName);
					if (hook === undefined) {
						const eventName = getEventName(hookName);
						hook = {
							tap(_, handler) {
								addEvent(eventName, handler);
							},
							tapAsync(_, handler) {
								addEvent(eventName, handler);
							},
							tapPromise(_, handler) {
								addEvent(eventName, handler);
							}
						};
						hooks.set(hookName, hook);
					}
					return hook;
				}
			})
		};
	};

	this.getEventBindings = function() {
		return events;
	};
};