Add ability to run only a specific module from CLI.

CONTRIBUTING.md

@@ -61,6 +61,10 @@ Our tests are based on [QUnit](https://qunitjs.com/) and [Puppeteer](https://git
 
     grunt test
 
+To test a specific module (`navigator` here) only:
+
+    grunt test --module="navigator"
+
 If you wish to work interactively with the tests or test your changes:
 
     grunt connect watch
@@ -69,6 +73,12 @@ and open `http://localhost:8000/test/test.html` in your browser.
 
 Another good page, if you want to interactively test out your changes, is `http://localhost:8000/test/demo/basic.html`.
 
+
+> Note: corresponding npm commands for the above are:
+>  - npm run test
+>  - npm run test -- --module="navigator"
+>  - npm run dev
+
 You can also get a report of the tests' code coverage:
 
     grunt coverage

Gruntfile.js

@@ -81,6 +81,11 @@ module.exports = function(grunt) {
         grunt.config.set('gitInfo', rev);
     });
 
+    let moduleFilter =  '';
+    if (grunt.option('module')) {
+        moduleFilter = '?module=' + grunt.option('module')
+    }
+
     // ----------
     // Project configuration.
     grunt.initConfig({
@@ -166,7 +171,7 @@ module.exports = function(grunt) {
         qunit: {
             normal: {
                 options: {
-                    urls: [ "http://localhost:8000/test/test.html" ],
+                    urls: [ "http://localhost:8000/test/test.html" + moduleFilter ],
                     timeout: 10000,
                     puppeteer: {
                         headless: 'new'
@@ -175,7 +180,7 @@ module.exports = function(grunt) {
             },
             coverage: {
                 options: {
-                    urls: [ "http://localhost:8000/test/coverage.html" ],
+                    urls: [ "http://localhost:8000/test/coverage.html" + moduleFilter ],
                     coverage: {
                         src: ['src/*.js'],
                         htmlReport: coverageDir + '/html/',