Check environment variable LOG4JS_CONFIG for configuration file location.

test/configuration-test.js

@@ -84,6 +84,48 @@ vows.describe('log4js configure').addBatch({
             'should add appender configure function to appenderMakers': function(log4js) {
                 assert.isFunction(log4js.appenderMakers['some/other/external']);
             }
+        },
+        'when configuration file loaded via LOG4JS_CONFIG environment variable': {
+          topic: function() {
+            process.env.LOG4JS_CONFIG = 'some/path/to/mylog4js.json';
+            var fileRead = 0,
+            modulePath = 'some/path/to/mylog4js.json',
+            pathsChecked = [],
+            mtime = new Date(),
+            fakeFS = {
+                config: { appenders: [ { type: 'console', layout: { type: 'messagePassThrough' } } ],
+                          levels: { 'a-test' : 'INFO' } },
+                readdirSync: function(dir) {
+                    return require('fs').readdirSync(dir);
+                },
+                readFileSync: function (file, encoding) {
+                    fileRead += 1;
+                    assert.isString(file);
+                    assert.equal(file, modulePath);
+                    assert.equal(encoding, 'utf8');
+                    return JSON.stringify(fakeFS.config);
+                },
+                statSync: function (path) {
+                    pathsChecked.push(path);
+                    if (path === modulePath) {
+                        return { mtime: mtime };
+                    } else {
+                        throw new Error("no such file");
+                    }
+                }
+            },
+            log4js = sandbox.require('../lib/log4js',
+                                     {
+                                       requires: {
+                                         'fs': fakeFS,
+                                       }
+                                     });
+
+            return fileRead;
+          },
+          'should load the specified local configuration file' : function(fileRead) {
+            assert.equal(fileRead, 1);
+          }
         }
     }
 }).exportTo(module);