Example of better way to manage flags and mocks

src/controllers/start.controller.ts

@@ -1,11 +1,18 @@
 import { NextFunction, Request, Response } from "express";
 
 import * as config from "../config";
+import { hasFeature } from "utils/feature.flag";
 
 export const get = (_req: Request, res: Response, _next: NextFunction) => {
   // example error message using the locales json files
   const errorMessage = res.locals.i18n["startPage"]["errorStartAddressMissing"];
 
+  if (hasFeature().FLAG_1) {
+    console.log("***** FLAG_1");
+  }
+  if (hasFeature().FLAG_2) {
+    console.log("***** FLAG_2");
+  }
   return res.render(config.START_TEMPLATE, {
     errorMessage
   });

src/test/flag.test.ts

@@ -0,0 +1,19 @@
+import app from "app";
+import request from "supertest";
+import * as config from "../config";
+import { hasFeature } from "../utils/feature.flag";
+
+jest.mock("../utils/feature.flag");
+
+(hasFeature as jest.Mock).mockReturnValue({
+  "FLAG_1": false,
+  "FLAG_2": true
+});
+
+describe("Experimental flags test", () => {
+  test("something", async () => {
+    await request(app).get(config.START_URL);
+
+    // check console to see what is logged
+  });
+});

src/test/global.setup.ts

@@ -17,4 +17,8 @@ export default () => {
   process.env.PIWIK_SITE_ID = "24";
   process.env.PIWIK_URL = "piwik.url";
   process.env.PORT = "3000";
+
+  process.env.FLAG_1 = "false";
+  process.env.FLAG_2 = "false";
+
 };

src/utils/feature.flag.ts

@@ -0,0 +1,12 @@
+import { getEnvironmentValueAsBoolean } from "./environment.value";
+
+type FeatureFlags = {
+    [key: string]: boolean
+}
+
+const flags: FeatureFlags = {
+  "FLAG_1": getEnvironmentValueAsBoolean("FLAG_1"),
+  "FLAG_2": getEnvironmentValueAsBoolean("FLAG_2")
+};
+
+export const hasFeature = (): FeatureFlags => flags;