feat(TestWorkers): Ability to Unit Test Workers (#23)

* feat(TestWorker): Add the ability to unit test a worker

* doc(TestWorker): Adding documentation on unit testing workers

Author: gja

README.md

@@ -1,5 +1,5 @@
 # cloudflare-worker-local
-WIP: Run a Cloudflare Worker Locally
+Run (or test) a Cloudflare Worker Locally
 
 ## Running
 
@@ -19,6 +19,10 @@ $ npm install -g nodemon
 $ nodemon --watch /path/to/worker.js --signal SIGHUP --exec 'cloudflare-worker-local /path/to/worker.js localhost:3000 4000'
 ```
 
+## Unit Testing a Cloudflare Worker
+
+`cloudflare-worker-local` can be used to unit test a cloudflare worker. Please see [This Example](examples/unit-test-a-worker)
+
 ## Things that are supported (and in scope)
 
 * Anything in Node.js scope by default (Object, Array)

app/__tests__/test-app_spec.js

@@ -0,0 +1,15 @@
+const { createTestApp } = require("../test-app");
+const express = require("express");
+const supertest = require("supertest");
+
+describe("server", () => {
+  it("returns the response from the worker", async () => {
+    const upstreamApp = express();
+    upstreamApp.get("/some-route", (req, res) => res.end("hello"));
+    const app = createTestApp('addEventListener("fetch", (e) => e.respondWith(fetch(e.request)))', upstreamApp);
+
+    await supertest(app)
+      .get("/some-route")
+      .expect(200, "hello");
+  });
+});

app/server.js

@@ -43,6 +43,10 @@ function createApp(workerContent, opts) {
     workerContent = contents;
     workersByOrigin = {};
   };
+  app.updateOpts = newOpts => {
+    opts = Object.assign({}, opts, newOpts);
+    workersByOrigin = {};
+  };
 
   return app;
 }

app/test-app.js

@@ -0,0 +1,23 @@
+const { createApp } = require("./server");
+const http = require("http");
+
+function createTestApp(workerContent, upstreamApp, opts = {}) {
+  const app = createApp(workerContent, opts);
+  const server = http.createServer(app);
+  const upstreamServer = http.createServer(upstreamApp);
+
+  server.listen = function() {
+    upstreamServer.listen(0);
+    app.updateOpts({ upstreamHost: `127.0.0.1:${upstreamServer.address().port}` });
+    return http.Server.prototype.listen.apply(this, arguments);
+  };
+
+  server.close = function() {
+    upstreamServer.close();
+    return http.Server.prototype.close.apply(this, arguments);
+  };
+
+  return server;
+}
+
+module.exports = { createTestApp };

examples/unit-test-a-worker/__tests__/worker_spec.js

@@ -0,0 +1,27 @@
+const { createTestApp } = require("cloudflare-worker-local");
+const supertest = require("supertest");
+const express = require("express");
+const fs = require("fs");
+
+const workerContent = fs.readFileSync(`${__dirname}/../worker.js`);
+
+describe("My New Worker", () => {
+  it("Adds a header on 200 responses", async () => {
+    const upstreamApp = express();
+    upstreamApp.get("/route", (req, res) => res.end("Success"));
+    await supertest(createTestApp(workerContent, upstreamApp))
+      .get("/route")
+      .expect("Foo", "Bar")
+      .expect(200, "Success");
+  });
+
+  it("Adds a different header on 404", async () => {
+    // all routes are 404
+    const upstreamApp = express();
+
+    await supertest(createTestApp(workerContent, upstreamApp))
+      .get("/route")
+      .expect("Foo", "Not Bar")
+      .expect(404);
+  });
+});

examples/unit-test-a-worker/worker.js

@@ -0,0 +1,15 @@
+addEventListener("fetch", e => {
+  e.respondWith(fetchAndAddHeader(e.request));
+});
+
+async function fetchAndAddHeader(request) {
+  const response = await fetch(request);
+
+  if (response.status === 200) {
+    response.headers.set("Foo", "Bar");
+  } else {
+    response.headers.set("Foo", "Not Bar");
+  }
+
+  return response;
+}

index.js

@@ -1,7 +1,9 @@
 const { createApp } = require("./app/server");
 const { Worker } = require("./app/worker");
+const { createTestApp } = require("./app/test-app");
 
 module.exports = {
   Worker,
-  createApp
+  createApp,
+  createTestApp
 };

package.json

@@ -37,5 +37,8 @@
   },
   "bin": {
     "cloudflare-worker-local": "./cli.js"
+  },
+  "jest": {
+    "testPathIgnorePatterns": ["/node_modules/", "/examples"]
   }
 }