add simple config util test

src/config/config.util.spec.ts

@@ -0,0 +1,17 @@
+import { environment } from '../environments/environment.prod';
+import { extendEnvironmentWithAppConfig } from './config.util';
+import { DefaultAppConfig } from './default-app-config';
+
+describe('Config Util', () => {
+  describe('extendEnvironmentWithAppConfig', () => {
+    it('should extend prod environment with app config', () => {
+      const appConfig = new DefaultAppConfig();
+      const originalMsToLive = appConfig.cache.msToLive.default;
+      expect(originalMsToLive).toEqual(15 * 60 * 1000); // 15 minute
+      const msToLive = 1 * 60 * 1000; // 1 minute
+      appConfig.cache.msToLive.default = msToLive;
+      extendEnvironmentWithAppConfig(environment, appConfig);
+      expect(environment.cache.msToLive.default).toEqual(msToLive);
+    });
+  });
+});