add a README url check for CircleCI

Author: NHibiki

.circleci/config.yml

@@ -12,4 +12,5 @@ jobs:
     steps:
       - checkout
       - run: npm install
+      - run: npm install node-fetch
       - run: npm test

README.md

@@ -1,5 +1,7 @@
 # Unit Testing and Continuous Integration
 
+[![CircleCI](https://circleci.com/gh/NHibiki-NYU/UnitTestingCI.svg?style=svg)](https://circleci.com/gh/NHibiki-NYU/UnitTestingCI)
+
 This repository is for sudents in the course to experiment with unit testing and continuous integration. It uses the testing framework [Jest](https://jestjs.io/) and [CircleCI](https://circleci.com/) as described in the video tutorials linked below.
 
 This repo is forked from [CodingTrain/TestingTestTest](https://github.com/CodingTrain/TestingTestTest).

sketch.test.js

@@ -1,4 +1,7 @@
 const { sum, sub, prod, digital_root, sum42, sayHelloTo, anomalyCode, nOfFibonacci } = require('./sketch');
+const fs = require("fs");
+const path = require("path");
+const fetch = require("node-fetch");
 
 // test('adds 1 + 2 to equal 3', () => {
 //   expect(sum(1, 2)).toBe(3);
@@ -97,3 +100,28 @@ test('anomalyCode thousand should be 50000', () => {
 test('the 20th number of fibonacci should be 6765', () => {
   expect(nOfFibonacci(20)).toBe(6765);
 })
+
+const testUrlInMarkdown = (file) => {
+  let markdown = fs.readFileSync(file).toString();
+  let urls = [];
+  let regExp = /\[([^\]]+)\]\(([^)]+)\)/g;
+  let result = null;
+  while (result = regExp.exec(markdown)) urls.push(result[2]);
+  return [urls.length, async () => {
+    for (let url of urls) {
+      if (url.includes("://") && !url.split("://")[0].includes("/")) {
+        // An External url
+        let res = await fetch(url);
+        if (![200, 301, 302].includes(res.status)) throw new Error(`External Link Test: ${url} with bad response code ${res.status}`);
+      } else {
+        if (!fs.existsSync(path.join(path.dirname(file), url))) throw new Error(`Internal Link Test: ${url} with not found error`);
+      }
+    }
+  }];
+}
+
+it('tests url avaliability in README.md', async () => {
+  let [testCount, testFunc] = testUrlInMarkdown("README.md");
+  jest.setTimeout(testCount * 5000);
+  return await testFunc();
+});