Only sends the changed config options.

test/test_env_go.js

 /*
 This file is part of the Juju GUI, which lets users view and manage Juju
 environments within a graphical interface (https://launchpad.net/juju-gui).
 Copyright (C) 2012-2013 Canonical Ltd.
 
 This program is free software: you can redistribute it and/or modify it under
 the terms of the GNU Affero General Public License version 3, as published by
 the Free Software Foundation.
 
 This program is distributed in the hope that it will be useful, but WITHOUT
@@ skipping 787 matching lines @@
     });
 
     it('must error if both data and config are passed', function() {
       assert.throws(
           function() {
             env.set_config('mysql', {'cfg-key': 'cfg-val'}, 'YAMLBEBAML');},
           'Exactly one of config and data must be provided');
     });
 
     it('can set a service config', function() {
-      env.set_config('mysql', {'cfg-key': 'cfg-val'});
+      // This also tests that it only sends the changed values
+      env.set_config('mysql', {
+        'cfg-key': 'cfg-val',
+        'unchanged': 'bar'
+      }, null, {
+        'cfg-key': 'foo',
+        'unchanged': 'bar'
+      });
       msg = conn.last_message();
       var expected = {
         Type: 'Client',
         Params: {
           ServiceName: 'mysql',
           Config: {
             'cfg-key': 'cfg-val'
           }
         },
         Request: 'ServiceSet',
@@ skipping 15 matching lines @@
         Params: {
           ServiceName: 'mysql',
           ConfigYAML: data
         }
       };
       assert.deepEqual(expected, msg);
     });
 
     it('handles failed set config', function() {
       var err, service_name;
-      env.set_config('yoursql', {}, null, function(evt) {
+      env.set_config('yoursql', {}, null, {}, function(evt) {
         err = evt.err;
         service_name = evt.service_name;
       });
       msg = conn.last_message();
       conn.msg({
         RequestId: msg.RequestId,
         Error: 'service "yoursql" not found'
       });
       assert.equal(err, 'service "yoursql" not found');
       assert.equal(service_name, 'yoursql');
@@ skipping 456 matching lines @@
       env.dispatch_result({
         RequestId: msg.RequestId,
         Error: 'badness',
         Response: {}
       });
     });
 
   });
 
 })();