fixed and simplified test

tests/unit/model/relationships/belongs-to-test.js

@@ -192,14 +192,10 @@ test("when response to saving a belongsTo is a success but includes changes that
 
   let user = store.peekRecord('user', '1');
 
-  assert.equal(get(user, 'tag.id'), '1', 'confirm local state');
-
   run(function() {
     user.set('tag', store.peekRecord('tag', '2'));
   });
 
-  assert.equal(get(user, 'tag.id'), '2', 'expected local state to reflect the last set');
-
   env.adapter.updateRecord = function() {
     return {
       type: 'user',
@@ -209,22 +205,8 @@ test("when response to saving a belongsTo is a success but includes changes that
   };
 
   run(function() {
-    user.save().then(assert.wait(function() {
-      assert.equal(get(user, 'tag.id'), '1', 'expected new server state to be applied');
-    }));
-  });
-
-  env.adapter.findRecord = function() {
-    return {
-      type: 'user',
-      id: '1',
-      tag: { type: 'tag', id: '1' }
-    };
-  };
-
-  run(function() {
-    user.reload().then(assert.wait(function() {
-      assert.equal(get(user, 'tag.id'), '1', 'expected new server state to be applied');
+    user.save().then(assert.wait(function(user) {
+      assert.equal(user.get('tag.id'), '1', 'expected new server state to be applied');
     }));
   });
 });