test: Use eslint-plugin-mocha for tests

This pulls in the eslint-plugin-mocha and enables its use when linting
tests. Because our existing tests do not always follow the Mocha
conventions, some mocha rules are disable for now. See #289

Author: kadler

.eslintrc.js

@@ -1,5 +1,8 @@
 module.exports = {
   extends: 'airbnb-base',
+  plugins: [
+    'mocha',
+  ],
   env: {
     node: true,
   },
@@ -15,12 +18,19 @@ module.exports = {
         node: true,
         mocha: true,
       },
+      extends: 'plugin:mocha/recommended',
       rules: {
         // These are set by airbnb-base, but go against Mocha conventions
         // See https://mochajs.org/#arrow-functions
         // and https://github.com/airbnb/javascript/issues/433
         'func-names': 'off',
         'prefer-arrow-callback': 'off',
+
+        // The following rules cause problems for our existing tests, so they are disabled for now:
+        'mocha/no-mocha-arrows': 'off',
+        'mocha/no-skipped-tests': 'off',
+        'mocha/no-hooks-for-single-case': 'off',
+        'mocha/no-identical-title': 'off',
       },
     },
   ],

package-lock.json

@@ -48,6 +48,7 @@
     "eslint": "^6.2.0",
     "eslint-config-airbnb-base": "^14.0.0",
     "eslint-plugin-import": "^2.18.2",
+    "eslint-plugin-mocha": "^7.0.1",
     "mocha": "^6.2.3",
     "sinon": "^7.4.1",
     "standard-version": "^7.0.0"