[REF] owl: reorganize src code in sub files

tests/core/event_bus.test.ts

@@ -0,0 +1,45 @@
+import { EventBus } from "../../src/core/event_bus";
+
+describe("event bus behaviour", () => {
+  test("can subscribe and be notified", () => {
+    const bus = new EventBus();
+    let notified = false;
+    bus.on("event", {}, () => (notified = true));
+    expect(notified).toBe(false);
+    bus.trigger("event");
+    expect(notified).toBe(true);
+  });
+
+  test("callbacks are called with proper 'this'", () => {
+    expect.assertions(1);
+    const bus = new EventBus();
+    const owner = {};
+    bus.on("event", owner, function(this: any) {
+      expect(this).toBe(owner);
+    });
+    bus.trigger("event");
+  });
+
+  test("throw error if callback is undefined", () => {
+    expect.assertions(1);
+    const bus = new EventBus();
+    expect(() => bus.on("event", {}, <any>undefined)).toThrow(`Missing callback`);
+  });
+
+  test("can unsubscribe", () => {
+    const bus = new EventBus();
+    let notified = false;
+    let owner = {};
+    bus.on("event", owner, () => (notified = true));
+    bus.off("event", owner);
+    bus.trigger("event");
+    expect(notified).toBe(false);
+  });
+
+  test("arguments are properly propagated", () => {
+    expect.assertions(1);
+    const bus = new EventBus();
+    bus.on("event", {}, (arg: any) => expect(arg).toBe("hello world"));
+    bus.trigger("event", "hello world");
+  });
+});