add mocking functions for tests

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", () => {
+
+})