added simple tests

Author: Alexey Litvinov

package.json

@@ -7,7 +7,9 @@
     "css-modules-loader-core": "0.0.11",
     "object-assign": "^3.0.0"
   },
-  "devDependencies": {},
+  "devDependencies": {
+    "mocha": "^2.2.5"
+  },
   "scripts": {
     "test": "mocha test"
   },

test/example.css

@@ -0,0 +1,4 @@
+.app
+{
+  background: #999;
+}

test/index.js

@@ -0,0 +1,31 @@
+describe('css-modules-require-hook', function () {
+  'use strict';
+
+  var assert = require('assert');
+  var styles;
+
+  before(function (done) {
+    // loading hook
+    require('..');
+
+    try {
+      styles = require('./example.css');
+      done();
+    } catch(e) {
+      done(e);
+    }
+  });
+
+  it('loaded an object from "example.css" as a module', function () {
+    assert.strictEqual(typeof styles, 'object');
+  });
+
+  it('module has the "app" key', function () {
+    assert(styles.hasOwnProperty('app'));
+  });
+
+  it('the value of the "app" key is not an empty string', function () {
+    assert.strictEqual(typeof styles.app, 'string', 'app\'s value is not a string');
+    assert(styles.app, 'app contains an empty string');
+  });
+});