Forbid exclusive tests (#94)

Forgetting to remove the `.only` method on a test can result in
a reduced test coverage.  Introduce a minimal ESLint config for tests
which checks for exclusive tests. No other linting rules are enabled for
now because our test files haven't been linted in the past and there's
a lot to fix.

Author: stasm

common.mk

@@ -15,7 +15,8 @@ all: lint test build
 dist: lint test build html
 
 lint:
-	@eslint --max-warnings 0 src/
+	@eslint --config $(ROOT)/eslint_src.json --max-warnings 0 src/
+	@eslint --config $(ROOT)/eslint_test.json --max-warnings 0 test/
 	@echo -e " $(OK) $@"
 
 test:

.eslintrc.json eslint_src.json.eslintrc.json renamed to eslint_src.json

@@ -0,0 +1,21 @@
+{
+    "parserOptions": {
+        "ecmaVersion": 8,
+        "sourceType": "module",
+        "ecmaFeatures": {
+            "jsx": true
+        }
+    },
+    "env": {
+        "es6": true,
+        "node": true,
+        "mocha": true
+    },
+    "plugins": [
+        "mocha"
+    ],
+    "rules": {
+        "mocha/no-exclusive-tests": "error",
+        "mocha/no-identical-title": "error"
+    }
+}

eslint_test.json

@@ -83,7 +83,7 @@ suite('Built-in functions', function() {
       assert.equal(ctx.format(msg), 'Invalid Date');
     });
 
-    test.only('Date argument', function() {
+    test('Date argument', function () {
       const date = new Date('2016-09-29');
       // format the date argument to account for the testrunner's timezone
       const expectedDefault =

fluent/test/functions_builtin_test.js

@@ -13,6 +13,7 @@
     "commander": "^2.9",
     "documentation": "^4.0.0-beta10",
     "eslint": "^3.19.0",
+    "eslint-plugin-mocha": "^4.11.0",
     "fuzzer": "^0.2.1",
     "gh-pages": "^0.12.0",
     "jsdoc": "^3.5.4",