feat: add basic test for emitter

test/emitter.test.ts

@@ -0,0 +1,52 @@
+import { Emitter } from "../src/common/emitter"
+
+describe("emitter", () => {
+  describe("Emitter", () => {
+    it("should return an Emitter", async () => {
+      const HELLO_WORLD = "HELLO_WORLD"
+      const GOODBYE_WORLD = "GOODBYE_WORLD"
+      const mockCallback = jest.fn(() => "Mock function called")
+      const mockSecondCallback = jest.fn(() => undefined)
+
+      const emitter = new Emitter<{ event: string; callback: () => void }>()
+
+      const onHelloWorld = ({ event, callback }: { event: string; callback: () => void }): void => {
+        if (event === HELLO_WORLD) {
+          callback()
+        }
+      }
+
+      const onGoodbyeWorld = ({ event, callback }: { event: string; callback: () => void }): void => {
+        if (event === GOODBYE_WORLD) {
+          callback()
+        }
+      }
+
+      // Register the onHelloWorld listener
+      // and the onGoodbyeWorld
+      emitter.event(onHelloWorld)
+      emitter.event(onGoodbyeWorld)
+
+      await emitter.emit({ event: HELLO_WORLD, callback: mockCallback })
+
+      // Double-check that our callback is called only once
+      expect(mockCallback).toHaveBeenCalled()
+      expect(mockCallback).toHaveBeenCalledTimes(1)
+
+      await emitter.emit({ event: GOODBYE_WORLD, callback: mockSecondCallback })
+
+      // Check that it works with multiple listeners
+      expect(mockSecondCallback).toHaveBeenCalled()
+      expect(mockSecondCallback).toHaveBeenCalledTimes(1)
+
+      // Dispose of all the listeners
+      emitter.dispose()
+    })
+
+    it.skip("should log an error if something goes wrong", () => {
+      // not sure how we're going to test this
+      // need to mock logger
+      // and then somehow throw or something in the callback
+    })
+  })
+})