test(pkg): Add tests to verify config

Use Jest as a testing framework to check that the required config
options are being set correctly. This also adds the Jest ESLint plugin
and includes its recommended rules.

.eslintrc.js

@@ -1,7 +1,14 @@
 module.exports = {
+  plugins: [
+    'jest'
+  ],
   extends: [
     'eslint:recommended',
+    'plugin:jest/recommended',
     'plugin:vue/recommended',
     'standard'
-  ]
+  ],
+  env: {
+    'jest/globals': true
+  }
 }

__mocks__/requireindex.js

@@ -0,0 +1,79 @@
+/* eslint-disable */
+
+/*
+ * This file mocks an old, outdated package on which `eslint-plugin-vue`
+ * depends. The `requireindex` dependency uses `require.extensions` to determine
+ * which files to include (or omit), but Jest injects its own `require` global
+ * that does not populate the `extensions` property. This bug causes
+ * `requireindex` to ignore all files when in the Jest testing environment.
+ *
+ * Related GitHub issues:
+ *  - https://github.com/facebook/jest/issues/2017
+ *  - https://github.com/vuejs/eslint-plugin-vue/issues/290
+ */
+
+var FS   = require('fs');
+var Path = require('path');
+
+module.exports = function (dir, basenames) {
+  var requires = {};
+
+  if (arguments.length === 2) {
+    // if basenames argument is passed, explicitly include those files
+    basenames.forEach(function (basename) {
+      var filepath = Path.resolve(Path.join(dir, basename));
+      requires[basename] = require(filepath);
+    });
+
+  } else if (arguments.length === 1) {
+    // if basenames arguments isn't passed, require all javascript
+    // files (except for those prefixed with _) and all directories
+
+    var files = FS.readdirSync(dir);
+
+    // sort files in lowercase alpha for linux
+    files.sort(function (a,b) {
+      a = a.toLowerCase();
+      b = b.toLowerCase();
+
+      if (a < b) {
+        return -1;
+      } else if (b < a) {
+        return 1;
+      } else {
+        return 0;
+      }
+    });
+
+    files.forEach(function (filename) {
+      // ignore index.js and files prefixed with underscore and
+      if ((filename === 'index.js') || (filename[0] === '_') || (filename[0] === '.')) {
+        return;
+      }
+
+      var filepath = Path.resolve(Path.join(dir, filename));
+      var ext      = Path.extname(filename);
+      var stats    = FS.statSync(filepath);
+
+      /*
+       * The next line of code has been patched to check that `ext` is any
+       * non-JavaScript extension directly, as `require.extensions` is empty
+       * when in the Jest testing environment.
+       */
+
+      // don't require non-javascript files (.txt .md etc.)
+      if (stats.isFile() && !['.js', '.json', '.node'].includes(ext)) {
+        return;
+      }
+
+      var basename = Path.basename(filename, ext);
+
+      requires[basename] = require(filepath);
+    });
+
+  } else {
+    throw new Error("Must pass directory as first argument");
+  }
+
+  return requires;
+};

__tests__/eslintrc.test.js

@@ -0,0 +1,23 @@
+const { CLIEngine } = require('eslint')
+
+const configFile = require.resolve('../.eslintrc')
+const engine = new CLIEngine({ configFile })
+
+test('includes required parser options', () => {
+  const config = engine.getConfigForFile(configFile)
+  expect(config.parserOptions.ecmaVersion).toBeGreaterThanOrEqual(6)
+  expect(config.parserOptions).toHaveProperty('sourceType', 'module')
+})
+
+test('includes required environments', () => {
+  const config = engine.getConfigForFile(configFile)
+  expect(config.env).toHaveProperty('browser', true)
+  expect(config.env).toHaveProperty('es6', true)
+  expect(config.env).toHaveProperty('node', true)
+})
+
+test('includes required plugins', () => {
+  const config = engine.getConfigForFile(configFile)
+  expect(config.plugins).toContain('jest')
+  expect(config.plugins).toContain('vue')
+})

package.json

@@ -13,18 +13,21 @@
   "main": ".eslintrc.js",
   "repository": "scriptdaemon/eslint-config",
   "scripts": {
-    "test": "eslint --ignore-pattern !.eslintrc.js ."
+    "lint": "eslint --ignore-pattern !.eslintrc.js .",
+    "test": "npm run lint && jest"
   },
   "dependencies": {
     "eslint-config-standard": "^10.2.1",
     "eslint-plugin-import": "^2.8.0",
+    "eslint-plugin-jest": "^21.4.3",
     "eslint-plugin-node": "^5.2.1",
     "eslint-plugin-promise": "^3.6.0",
     "eslint-plugin-standard": "^3.0.1",
     "eslint-plugin-vue": "^4.0.0-beta.2"
   },
   "devDependencies": {
-    "eslint": "^4.12.1"
+    "eslint": "^4.12.1",
+    "jest": "^21.2.1"
   },
   "peerDependencies": {
     "eslint": "^4.12.1"