Introduce UserHiveVisitor for performing operations on local users' registry hives.

chrome/installer/setup/user_hive_visitor_unittest.cc

Index: chrome/installer/setup/user_hive_visitor_unittest.cc
diff --git a/chrome/installer/setup/user_hive_visitor_unittest.cc b/chrome/installer/setup/user_hive_visitor_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..19eb0172e2af09759f225638c856263c4fccb81b
--- /dev/null
+++ b/chrome/installer/setup/user_hive_visitor_unittest.cc
@@ -0,0 +1,70 @@
+// 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 "chrome/installer/setup/user_hive_visitor.h"
+
+#include <vector>
+
+#include "base/bind.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/win/registry.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace installer {
+
+namespace {
+
+class UserHiveVisitor {
+ public:
+  UserHiveVisitor() = default;
+
+  bool OnUserHive(const wchar_t* sid, base::win::RegKey* key) {
+    EXPECT_NE(nullptr, sid);
+    EXPECT_STRNE(L"", sid);
+    EXPECT_NE(nullptr, key);
+    EXPECT_TRUE(key->Valid());
+    sids_visited_.push_back(sid);
+    return !max_count_ ? true : (sids_visited_.size() < max_count_);

[gab, 2016/06/01 16:17:04]

So |max_count_| is always 0 or 1. Make it a bool?

+  }
+
+  void set_max_count(int count) { max_count_ = count; }
+
+  const std::vector<base::string16> sids_visited() const {
+    return sids_visited_;
+  }
+
+ private:
+  std::vector<base::string16> sids_visited_;
+  size_t max_count_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(UserHiveVisitor);
+};
+
+}  // namespace
+
+// Tests that the visitor visits at least one user hive. This will succeed even
+// when run as an ordinary user, as the current user's hive is always available.
+TEST(UserHiveVisitorTest, VisitAllUserHives) {
+  UserHiveVisitor visitor;
+
+  VisitUserHives(
+      base::Bind(&UserHiveVisitor::OnUserHive, base::Unretained(&visitor)));
+
+  EXPECT_LT(0U, visitor.sids_visited().size());

[gab, 2016/06/01 16:17:04]

Inequalities are more readable with constant on RHS IMO.

[grt (UTC plus 2), 2016/06/01 18:00:47]

Okay. I had done it this way for consistency with EXPECT_EQ and EXPECT_NE, which
are documented as taking the "expected" value on the LHS.

[gab, 2016/06/03 15:13:08]

Right but reading inequalities backward is so weird that I prefer the
inconsistency.

Alternatively since this is unsigned you could EXPECT_NE(0U, ...size());

[grt (UTC plus 2), 2016/06/06 01:10:11]

I agreed with your logic and changed it as you requested. My remark was just
explaining the original code, not pushing back on the request. :-)

+}
+
+// Tests that only one user hive is visited when the visitor returns false to
+// stop the iteration.
+TEST(UserHiveVisitor, VisitOneHive) {
+  UserHiveVisitor visitor;
+
+  visitor.set_max_count(1);
+  VisitUserHives(
+      base::Bind(&UserHiveVisitor::OnUserHive, base::Unretained(&visitor)));
+
+  EXPECT_EQ(1U, visitor.sids_visited().size());
+}
+
+}  // namespace installer