test method
Test functionality, run EventNotifier.test()
Implementation
static void test() {
var e = EventNotifier();
e.subscribe('myChange', (_) => print('boom'));
e.subscribe('myChange', (args) => print(args['pi']));
// number of event names
assert(e.count() == 1);
// number of handlers subscribed to the event name
assert(e.count('myChange') == 2);
// indicate that event 'myChange' has occured
// rguments are only required if a subscriber
// expects one or more
e.notify('myChange', {'pi': 3.14159});
// displays ...
// boom
// 3.14159
}