Merge pull request #6 from scraggo/shuffle-order

Shuffle order

Author: scraggo

.eslintrc.json

@@ -1,6 +1,7 @@
 {
   "extends": ["airbnb-base", "plugin:prettier/recommended"],
   "plugins": ["prettier"],
+  "root": true,
   "rules": {
     "import/prefer-default-export": 0,
     "prettier/prettier": "error"

README.md

@@ -506,6 +506,7 @@ Found a typo? Want to add details or make a correction? This repo is open-source
 Articles:
 
 - [Node.js & JavaScript Testing Best Practices (2020) - Medium](https://medium.com/@me_37286/yoni-goldberg-javascript-nodejs-testing-best-practices-2b98924c9347)
+- [An Overview of JavaScript Testing in 2020 - Medium](https://medium.com/welldone-software/an-overview-of-javascript-testing-7ce7298b9870)
 - <https://npmcompare.com/compare/ava,jest,mocha,mocha-parallel-tests>
 - <https://www.slant.co/versus/12696/12697/~mocha_vs_jest>
 - <https://stackshare.io/stackups/ava-vs-mocha>
@@ -524,7 +525,7 @@ More on Jest:
 
 More on AVA:
 
-- <https://github.com/avajs/awesome-ava#readme>
+- <https://github.com/avajs/awesome-ava>
 - <http://zpalexander.com/migrating-from-mocha-to-ava/>
 - [AVA, low-config testing for JavaScript - hello JS](https://blog.hellojs.org/ava-low-config-testing-for-javascript-71bd2d958745)
 - [Ava Test Runner - A Fresh Take On JavaScript Testing and Growing an Open-Source Project - Sessions by Pusher](https://pusher.com/sessions/meetup/the-js-roundabout/ava-test-runner-a-fresh-take-on-javascript-testing-and-growing-an-open-source-project)

docs/test-runner.md

@@ -22,6 +22,10 @@ This application is a test-runner that can:
 
 The number and length of the authored tests simulate a "true" test run in a significantly sized enterprise codebase. Each test runner has a template that will run the _same exact_ test blocks and take the _same exact_ amount of time in each block. (This is done with a `setTimeout` with a time that increases with each iteration of the loop that generates the test block.)
 
+To account for a bias in ordering, the scripts corresponding to each test runner are shuffled. This ensures that the suites for each test runner are never called in the same sequence.
+
+![speed-test-results.png](../images/speed-test-results.png)
+
 ## Running the tests
 
 `npm install` to install all the packages.

images/speed-test-results.png

@@ -1,7 +1,9 @@
 const { fullCircle } = require('./fullCircle');
 const { range } = require('./range');
+const { shuffle } = require('./shuffle');
 
 module.exports = {
   fullCircle,
   range,
+  shuffle,
 };

src/index.js

@@ -1,8 +1,11 @@
 const execa = require('execa');
+const { shuffle } = require('./');
 
 // CONSTANTS
 
-const testRunners = ['ava', 'jest', 'mocha', 'parallel'];
+const TEST_RUNNERS = ['ava', 'jest', 'mocha', 'parallel'];
+const DOTS = '. '.repeat(16);
+const testRunners = shuffle(TEST_RUNNERS);
 
 // UTILS
 
@@ -59,6 +62,10 @@ const runScript = scriptObj => {
   return Date.now() - start;
 };
 
+const logTestTitle = name => {
+  console.log('\n\n', DOTS, '\n   running tests for', name, '\n', DOTS, '\n\n');
+};
+
 // sort, format, and log test results
 const logResults = resultsArr => {
   resultsArr
@@ -96,16 +103,16 @@ const main = () => {
     for (const name of testRunners) {
       const { run } = testData[name];
 
-      console.log('running tests for', name, '\n. . . . . . . . ');
+      logTestTitle(name);
 
       testData[name].executionTime = run();
       testResults.push(testData[name]);
     }
 
     console.log(`-*-*-*-*-*-*-*-*-*-*-
       RESULTS
--*-*-*-*-*-*-*-*-*-*-`);
-
+-*-*-*-*-*-*-*-*-*-*-\n`);
+    console.log('order:', testRunners, '\n');
     logResults(testResults);
   } catch (error) {
     console.error(error);

src/runAllTests.js

@@ -0,0 +1,19 @@
+/**
+ * Fisher Yates Shuffle
+ * @param {Array} arrInput
+ * @param {Object} [options={}]
+ * @param {boolean} [options.clone=false]
+ * @returns {Array} shuffled array
+ */
+function shuffle(arrInput, { clone = false } = {}) {
+  const arr = clone ? arrInput.slice() : arrInput;
+
+  for (let i = arr.length - 1; i > 0; i -= 1) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [arr[i], arr[j]] = [arr[j], arr[i]];
+  }
+
+  return arr;
+}
+
+module.exports = { shuffle };

src/shuffle.js

@@ -0,0 +1,8 @@
+{
+  "rules": {
+    "func-names": 0
+  },
+  "globals": {
+    "expect": true
+  }
+}

test/src/.eslintrc.json

@@ -1,5 +1,3 @@
-// const { expect } = require('chai');
-
 const { range } = require('../../src');
 
 describe('range', function() {
@@ -17,9 +15,9 @@ describe('range', function() {
     expect(res).to.deep.equal([]);
   });
   it('throws error under bad conditions', function() {
-    expect(() => range()).to.throw;
-    expect(() => range(-1)).to.throw;
-    expect(() => range(-2, -1)).to.throw;
-    expect(() => range(2, 1)).to.throw;
+    expect(() => range()).to.throw();
+    expect(() => range(-1)).to.throw();
+    expect(() => range(-2, -1)).to.throw();
+    expect(() => range(2, 1)).to.throw();
   });
 });

test/src/range.spec.js

@@ -0,0 +1,17 @@
+const { range, shuffle } = require('../../src');
+
+describe('shuffle', function() {
+  it('returns array of same length', function() {
+    expect(shuffle([0, 1])).to.have.length(2);
+    expect(shuffle([0, 1, 2])).to.have.length(3);
+    expect(shuffle([0, 1, 2, 3])).to.have.length(4);
+  });
+
+  it('eventually shuffles cloned array', function() {
+    const arr = [0, 1];
+    const NUM_OF_RUNS = 5;
+    const runs = range(0, NUM_OF_RUNS).map(() => shuffle(arr, { clone: true }));
+
+    expect(runs).to.deep.include([1, 0]);
+  });
+});