refactor event handling to consume base class for lifecycling

tests/unit/infrastructure/Events/EventSubscriptionCollection.spec.ts

@@ -0,0 +1,22 @@
+import { EventSubscriptionCollection } from '@/infrastructure/Events/EventSubscriptionCollection';
+import { IEventSubscription } from '@/infrastructure/Events/IEventSource';
+import { expect } from 'chai';
+import 'mocha';
+
+describe('EventSubscriptionCollection', () => {
+    it('unsubscribeAll unsubscribes from all registered subscriptions', () => {
+        // arrange
+        const sut = new EventSubscriptionCollection();
+        const expected = [ 'unsubscribed1', 'unsubscribed2'];
+        const actual = new Array<string>();
+        const subscriptions: IEventSubscription[] = [
+            { unsubscribe: () => actual.push(expected[0]) },
+            { unsubscribe: () => actual.push(expected[1]) },
+        ];
+        // act
+        sut.register(...subscriptions);
+        sut.unsubscribeAll();
+        // assert
+        expect(actual).to.deep.equal(expected);
+    });
+});