add mocking functions for tests

src/repositories/ApiBasedRepository.ts

@@ -1,16 +1,14 @@
 import { GetterRepository } from "./GetterRepository";
 import { IEta } from "../entities/entities";
 
+// TODO: implement
+
 export class ApiBasedRepository implements GetterRepository {
   public async getEtaForShuttleAndStopId(shuttleId: string, stopId: string): Promise<IEta | null> {
-    // TODO: implement
-
     return null;
   }
 
   public async getEtasForShuttleId(shuttleId: string): Promise<[]> {
-    // TODO: implement
-
     return [];
   }
 

test/repositories/ApiBasedRepositoryTests.ts

@@ -0,0 +1,40 @@
+import { beforeEach, describe, jest, test } from "@jest/globals";
+
+/**
+ * Update the global fetch function to return a specific object.
+ * @param obj
+ */
+function updateGlobalFetchMockJson(obj: any) {
+  // @ts-ignore
+  global.fetch = jest.fn(() => {
+    return Promise.resolve({
+      json: () => Promise.resolve(obj)
+    })
+  }) as jest.Mock;
+}
+
+/**
+ * Reset the global fetch function mock's JSON to return an empty object.
+ * @param obj
+ */
+function resetGlobalFetchMockJson() {
+  updateGlobalFetchMockJson({})
+}
+
+beforeEach(() => {
+  resetGlobalFetchMockJson();
+})
+
+describe("getEtaForShuttleAndStopId", () => {
+  test("getEtaForShuttleAndStopId returns correct ETA data", async () => {
+
+  });
+
+  test("getEtaForShuttleAndStopId returns null if API call is invalid", async () => {
+
+  });
+});
+
+describe("getEtasForShuttleId", () => {
+
+})