Handle absolute/invalid paths in the configuration

Author: Rohan Jain

browserstack.sample.json

@@ -1,7 +1,7 @@
 {
   "username": "<username>",
   "key": "<key>",
-  "test_path": "path/to/test/page",
+  "test_path": "relative/path/to/test/page",
   "browsers":   [{
     "browser": "firefox",
     "browser_version": "15.0",

lib/config.js

@@ -1,8 +1,12 @@
+var path = require('path'),
+    fs = require('fs');
+var pwd = process.cwd();
+
 try {
   var config = require(process.cwd() + '/browserstack');
 } catch (e) {
   if (e.code == 'MODULE_NOT_FOUND') {
-    console.log('Configuration file `browserstack.json` is missing.');
+    console.error('Configuration file `browserstack.json` is missing.');
   } else {
     throw(e);
   }
@@ -18,6 +22,23 @@ if (process.env.BROWSERSTACK_USERNAME) {
   config.username = process.env.BROWSERSTACK_USERNAME;
 }
 
+['username', 'key', 'test_path', 'browsers'].forEach(function (param) {
+  if (typeof config[param] === 'undefined') {
+    console.error('Configuration parameter `%s` is required.', param);
+    process.exit(1);
+  }
+});
+
+// Convert absoulte path into relative paths.
+if (config.test_path.indexOf(pwd) === 0) {
+  config.test_path = config.test_path.slice(pwd.length + 1);
+}
+
+if (!fs.existsSync(config.test_path)){
+  console.error('Test path is invalid.');
+  process.exit(1);
+}
+
 for (key in config) {
   if (config.hasOwnProperty(key)) {
     exports[key] = config[key];