Fix tests

routes/weather.spec.ts

@@ -4,6 +4,10 @@ import * as MockExpressRequest from 'mock-express-request';
 import * as MockExpressResponse from 'mock-express-response';
 import * as MockDate from 'mockdate';
 
+// The tests don't use OWM, but the WeatherProvider API key must be set to prevent an error from being thrown on startup.
+process.env.WEATHER_PROVIDER = "OWM";
+process.env.OWM_API_KEY = "NO_KEY";
+
 import { getWateringData } from './weather';
 import { GeoCoordinates, WateringData, WeatherData } from "../types";
 import { WeatherProvider } from "./weatherProviders/WeatherProvider";