diff --git a/src/repositories/ApiBasedRepository.ts b/src/repositories/ApiBasedRepository.ts
index 18a562e..bf41eb6 100644
--- a/src/repositories/ApiBasedRepository.ts
+++ b/src/repositories/ApiBasedRepository.ts
@@ -1,5 +1,5 @@
 import { GetterRepository } from "./GetterRepository";
-import { IEta, IOrderedStop, IRoute, IShuttle, IStop } from "../entities/entities";
+import { IEta, IOrderedStop, IRoute, IShuttle, IStop, ISystem } from "../entities/entities";
 
 export interface ApiBasedRepositoryCache {
   etasForShuttleId?: {
@@ -39,6 +39,20 @@ export class ApiBasedRepository implements GetterRepository {
   ) {
   }
 
+  /**
+   * Seed the initial data in the cache, so data can be updated
+   * given the correct ID.
+   * Alternatively, pass in an `initialCache` with existing data
+   * (useful for testing).
+   * @param systemId
+   */
+  public async seedCacheForSystemId(systemId: string): Promise<void> {
+    await this.getShuttlesBySystemId(systemId);
+    await this.getShuttlesByRouteId(systemId);
+    await this.getStopsBySystemId(systemId);
+    await this.getSystemById(systemId);
+  }
+
   public async getEtaForShuttleAndStopId(shuttleId: string, stopId: string): Promise<IEta | null> {
     const shuttle = await this.getShuttleById(shuttleId);
     const systemId = shuttle?.systemId;
@@ -110,7 +124,7 @@ export class ApiBasedRepository implements GetterRepository {
     return [];
   }
 
-  public async getSystemById(systemId: string): Promise<| null> {
+  public async getSystemById(systemId: string): Promise<ISystem| null> {
     return null;
   }