3rd party services isolation/8 (goldbergyoni#20)

Author: Michael Solomon

.gitignore

@@ -102,3 +102,6 @@ dist
 
 # TernJS port file
 .tern-port
+
+# VSCode
+.vscode

example-application/api-under-test.js

@@ -81,11 +81,11 @@ const defineRoutes = (expressApp) => {
 
   expressApp.use("/order", router);
 
-  expressApp.use((err, req, res, next) => {
+  expressApp.use(async (err, req, res, next) => {
     console.log(err);
     if (process.env.SEND_MAILS === "true") {
       // important notification logic here
-      mailer.send();
+      await mailer.send('Error', err.message, 'admin@app.com');
 
       // Other important notification logic here
     }

example-application/libraries/mailer.js

@@ -1,3 +1,6 @@
-module.exports.send = (subject, body, recipientAddress) => {
+const axios = require('axios');
+
+module.exports.send = async (subject, body, recipientAddress) => {
   console.log('Not really a mailer, right?', subject, body, recipientAddress);
+  await axios.post(`https://mailer.com/send`, { subject, body, recipientAddress });
 };

example-application/test/basic-tests.test.js

@@ -98,6 +98,7 @@ describe("/api", () => {
         id: 1,
         name: "John",
       });
+      nock("http://localhost/").post(`/mailer`).reply(202);
       sinonSandbox.stub(OrderRepository.prototype, "addOrder").throws(new Error("Unknown error"));
       const spyOnMailer = sinon.spy(mailer, "send");
       const orderToAdd = {

various-receipes/3rd-party-services-isolation/test/isolation.test.js

@@ -0,0 +1,118 @@
+const request = require("supertest");
+const sinon = require("sinon");
+const nock = require("nock");
+const {
+  initializeWebServer,
+  stopWebServer
+} = require("../../../example-application/api-under-test");
+const OrderRepository = require("../../../example-application/data-access/order-repository");
+
+let expressApp;
+let sinonSandbox;
+
+beforeAll(async (done) => {
+  // ️️️✅ Best Practice: Place the backend under test within the same process
+  expressApp = await initializeWebServer();
+  // ️️️✅ Best Practice: Ensure that this component is isolated by preventing unknown calls except for the Api-Under-Test
+  nock.disableNetConnect();
+  nock.enableNetConnect('127.0.0.1');
+
+  // ️️️✅ Best Practice: use a sandbox for test doubles for proper clean-up between tests
+  sinonSandbox = sinon.createSandbox();
+
+  done();
+});
+
+afterAll(async (done) => {
+  // ️️️✅ Best Practice: Clean-up resources after each run
+  await stopWebServer();
+  done();
+});
+
+beforeEach(() => {
+  // ️️️✅ Best Practice: Isolate the service under test by intercepting requests to 3rd party services
+  nock("http://localhost/user/").get(`/1`).reply(200, {
+    id: 1,
+    name: "John",
+  })
+
+  if (sinonSandbox) {
+    sinonSandbox.restore();
+  }
+});
+
+afterEach(() => {
+  // ️️️✅ Best Practice: Clean nock interceptors between tests
+  nock.cleanAll();
+})
+
+// ️️️✅ Best Practice: Structure tests 
+describe("/api", () => {
+  describe("POST /orders", () => {
+    test("When adding  a new valid order , Then should get back 200 response", async () => {
+      //Arrange
+      const orderToAdd = {
+        userId: 1,
+        productId: 2,
+        mode: "approved",
+      };
+
+      //Act
+      // ➿ Nock intercepts the request for users service as declared in the BeforeAll function
+      const orderAddResult = await request(expressApp).post("/order").send(orderToAdd);
+
+      //Assert
+      expect(orderAddResult.status).toBe(200);
+    });
+
+    test("When the user does not exist, return http 404", async () => {
+      //Arrange
+      // ️️️✅ Best Practice: Simulate 3rd party service responses to test different scenarios like 404, 422 or 500.
+      //                    Use specific params (like ids) to easily bypass the beforeEach interceptor.
+      nock("http://localhost/user/").get(`/7`).reply(404, {
+        message: "User does not exist",
+        code: "nonExisting",
+      });
+      const orderToAdd = {
+        userId: 7,
+        productId: 2,
+        mode: "draft",
+      };
+
+      //Act
+      const orderAddResult = await request(expressApp)
+        .post("/order")
+        .send(orderToAdd)
+
+      //Assert
+      expect(orderAddResult.status).toBe(404);
+    });
+
+    test("When order failed, send mail to admin", async () => {
+      //Arrange
+      process.env.SEND_MAILS = "true";
+      sinonSandbox.stub(OrderRepository.prototype, "addOrder").throws(new Error("Unknown error"));
+      // ️️️✅ Best Practice: Intercept requests for 3rd party services to eliminate undesired side effects like emails or SMS
+      // ️️️✅ Best Practice: Specify the body when you need to make sure you call the 3rd party service as expected 
+      const scope = nock("https://mailer.com")
+        .post('/send', {
+          subject: /^(?!\s*$).+/, 
+          body: /^(?!\s*$).+/, 
+          recipientAddress: /^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$/,
+        })
+        .reply(202);
+      const orderToAdd = {
+        userId: 1,
+        productId: 2,
+        mode: "approved",
+      };
+
+      //Act
+      await request(expressApp).post("/order").send(orderToAdd);
+
+      //Assert
+      // ️️️✅ Best Practice: Assert that the app called the mailer service appropriately
+      expect(scope.isDone()).toBe(true);
+    });
+  });
+});