[Chromoting] GetHostAttributes with tests

remoting/host/host_attributes_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/host_attributes.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace remoting {
+
+// Ensures there is no DCHECK failure or crash in Register() and Callbacks.
+TEST(HostAttributesTest, Sanity) {
+  HostAttributes().ToString();
+}
+
+TEST(HostAttributesTest, DynamicValuesShouldBeEvaluated) {
+  const char key[] = "A-Fake-Trait-Key-In-Host-Traits-Unit-Test";
+  bool value = false;
+  int evaluated_times = 0;
+
+  HostAttributes host_attributes;
+  host_attributes.Register(
+      key, base::Bind(
+               [](int* evaluated_times, bool* value) {
+                 (*evaluated_times)++;
+                 return *value;
+               },
+               &evaluated_times, &value));
+
+  std::string result = host_attributes.ToString();
+  ASSERT_FALSE(HostAttributes::ContainsAttribute(result, key));
+  ASSERT_EQ(evaluated_times, 1);
+
+  value = true;
+  result = host_attributes.ToString();
+  ASSERT_TRUE(HostAttributes::ContainsAttribute(result, key));
+  ASSERT_EQ(evaluated_times, 2);
+}
+
+}  // namespace remoting