diff --git a/test/loaders/ApiBasedRepositoryLoaderTests.test.ts b/test/loaders/ApiBasedRepositoryLoaderTests.test.ts
index bc8000d..adc48eb 100644
--- a/test/loaders/ApiBasedRepositoryLoaderTests.test.ts
+++ b/test/loaders/ApiBasedRepositoryLoaderTests.test.ts
@@ -3,6 +3,7 @@ import { ApiBasedRepositoryLoader, ApiResponseError } from "../../src/loaders/Ap
 import { UnoptimizedInMemoryRepository } from "../../src/repositories/UnoptimizedInMemoryRepository";
 import { fetchSystemDataSuccessfulResponse } from "../jsonSnapshots/fetchSystemData/fetchSystemDataSuccessfulResponse";
 import { fetchSystemDataFailedResponse } from "../jsonSnapshots/fetchSystemData/fetchSystemDataFailedResponse";
+import { fetchRouteDataSuccessfulResponse } from "../jsonSnapshots/fetchRouteData/fetchRouteDataSuccessfulResponse";
 
 /**
  * Function to update behavior of the global `fetch` function.
@@ -76,13 +77,40 @@ describe("ApiBasedRepositoryLoader", () => {
     });
   });
 
-  describe("fetchAndUpdateRouteDataForExistingSystems", () => {
-    it("updates route data in repository if there are systems and response received", async () => {
 
+  describe("fetchAndUpdateRouteDataForExistingSystemsInRepository", () => {
+    // TODO
+    // Add a test case to ensure that fetchAndUpdateRouteDataForSystemId
+    // was called for every available system ID
+  });
+
+  describe("fetchAndUpdateRouteDataForSystemId", () => {
+    it("updates route data in repository if there are systems and response received", async () => {
+      updateGlobalFetchMockJson(fetchRouteDataSuccessfulResponse);
+
+      await loader.fetchAndUpdateRouteDataForSystemId("263");
+
+      const routes = await loader.repository.getRoutesBySystemId("263");
+
+      expect(routes.length).toEqual(fetchRouteDataSuccessfulResponse.all.length)
     });
 
     it("throws the correct error if the API response contains no data", async () => {
+      // The Passio API returns some invalid JSON if there is no data,
+      // so simulate a JSON parsing error
 
+      // @ts-ignore
+      global.fetch = jest.fn(() => {
+        return Promise.resolve({
+          json: () => Promise.reject(new SyntaxError("Unable to parse JSON")),
+          status: 200,
+          ok: true,
+        })
+      }) as jest.Mock;
+
+      await assertAsyncCallbackThrowsApiResponseError(async () => {
+        await loader.fetchAndUpdateRouteDataForSystemId("263");
+      });
     });
   });