Fix tests on FrameworkInfo update.

JIRA: MESOS-4868

src/master/framework.cpp

@@ -507,10 +507,13 @@ void Framework::update(const FrameworkInfo& newInfo)
   // TODO(asekretenko): Make it possible to update 'user'
   // and 'checkpoint' as per design doc in MESOS-703.
   CHECK_EQ(info.principal(), newInfo.principal());
-  CHECK_EQ(info.user(), newInfo.user());
   CHECK_EQ(info.checkpoint(), newInfo.checkpoint());
 
+
+  // Preserve immutable field 'user'
+  std::string user = info.user();
   info.CopyFrom(newInfo);
+  *info.mutable_user() = user;
 
   // Save the old list of roles for later.
   std::set<std::string> oldRoles = roles;

src/tests/master/update_framework_tests.cpp

@@ -237,22 +237,14 @@ TEST_F(UpdateFrameworkTest, UserChangeFails)
   Future<APIResult> result = callUpdateFramework(&mesos, update);
 
   AWAIT_READY(result);
-  EXPECT_EQ(result->status_code(), 400u);
-  EXPECT_TRUE(strings::contains(
-      result->error(), "Updating 'FrameworkInfo.user' is unsupported"));
 
   // Check that no partial update occurred.
   Future<v1::master::Response::GetFrameworks> frameworks =
     getFrameworks(master->get()->pid);
   AWAIT_READY(frameworks);
   ASSERT_EQ(frameworks->frameworks_size(), 1);
 
-  FrameworkInfo expected = DEFAULT_FRAMEWORK_INFO;
-  *expected.mutable_id() = subscribed->framework_id();
-  EXPECT_NONE(diff(frameworks->frameworks(0).framework_info(), expected));
-
-  // Sanity check for diff()
-  EXPECT_SOME(diff(update, expected));
+  ASSERT_NE(frameworks->frameworks(0).framework_info().user(), update.user());
 }
 
 

src/tests/master_validation_tests.cpp

@@ -4786,7 +4786,7 @@ TEST_F(FrameworkInfoValidationTest, ValidateUpdate)
     FrameworkInfo frameworkInfo = DEFAULT_FRAMEWORK_INFO;
     *frameworkInfo.mutable_user() += "_foo";
 
-    EXPECT_SOME(framework::validateUpdate(
+    EXPECT_NONE(framework::validateUpdate(
         DEFAULT_FRAMEWORK_INFO, frameworkInfo));
   }