update getEtaForShuttleAndStopId test to use method stubs

test/repositories/ApiBasedRepositoryTests.test.ts

@@ -4,7 +4,7 @@ import {
   ApiBasedRepositoryCache,
   ApiBasedRepositoryMillisecondTTLs
 } from "../../src/repositories/ApiBasedRepository";
-import { IEta } from "../../src/entities/entities";
+import { IEta, IShuttle } from "../../src/entities/entities";
 
 /**
  * Update the global fetch function to return a specific object.
@@ -254,7 +254,38 @@ describe("getEtaForShuttleAndStopId", () => {
   test("getEtaForShuttleAndStopId returns correct ETA data", async () => {
     updateGlobalFetchMockJson(genericEtaDataByStopId);
 
-    const repository = new ApiBasedRepository();
+    const initialCache: ApiBasedRepositoryCache = {
+      etasForStopId: {
+        "177666": [
+          {
+            secondsRemaining: 587,
+            shuttleId: "5577",
+            stopId: "177666",
+            millisecondsSinceEpoch: Date.now(),
+          }
+        ],
+      },
+    }
+
+    const repository = new ApiBasedRepository(initialCache);
+
+    repository.getShuttleById = jest.fn(async () => {
+      const shuttle: IShuttle = {
+        id: "5577",
+        name: "08",
+        coordinates: {
+          latitude: 33.7933406,
+          longitude: -117.8539321,
+        },
+        routeId: "53966",
+        systemId: "1",
+      };
+      return shuttle;
+    });
+
+    repository.updateEtasForSystemIfTTL = jest.fn(async () => {
+    });
+
     const result = await repository.getEtaForShuttleAndStopId("5577", "177666");
 
     expect(result?.secondsRemaining).toEqual(587);