diff --git a/absl/flags/commandlineflag_test.cc b/absl/flags/commandlineflag_test.cc
new file mode 100644
index 0000000..585db4b
--- /dev/null
+++ b/absl/flags/commandlineflag_test.cc
@@ -0,0 +1,231 @@
+//
+//  Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/flags/commandlineflag.h"
+
+#include <memory>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/flags/flag.h"
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/internal/private_handle_accessor.h"
+#include "absl/flags/reflection.h"
+#include "absl/flags/usage_config.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/match.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+ABSL_FLAG(int, int_flag, 201, "int_flag help");
+ABSL_FLAG(std::string, string_flag, "dflt",
+          absl::StrCat("string_flag", " help"));
+ABSL_RETIRED_FLAG(bool, bool_retired_flag, false, "bool_retired_flag help");
+
+// These are only used to test default values.
+ABSL_FLAG(int, int_flag2, 201, "");
+ABSL_FLAG(std::string, string_flag2, "dflt", "");
+
+namespace {
+
+namespace flags = absl::flags_internal;
+
+class CommandLineFlagTest : public testing::Test {
+ protected:
+  static void SetUpTestSuite() {
+    // Install a function to normalize filenames before this test is run.
+    absl::FlagsUsageConfig default_config;
+    default_config.normalize_filename = &CommandLineFlagTest::NormalizeFileName;
+    absl::SetFlagsUsageConfig(default_config);
+  }
+
+  void SetUp() override { flag_saver_ = absl::make_unique<absl::FlagSaver>(); }
+  void TearDown() override { flag_saver_.reset(); }
+
+ private:
+  static std::string NormalizeFileName(absl::string_view fname) {
+#ifdef _WIN32
+    std::string normalized(fname);
+    std::replace(normalized.begin(), normalized.end(), '\\', '/');
+    fname = normalized;
+#endif
+    return std::string(fname);
+  }
+
+  std::unique_ptr<absl::FlagSaver> flag_saver_;
+};
+
+TEST_F(CommandLineFlagTest, TestAttributesAccessMethods) {
+  auto* flag_01 = absl::FindCommandLineFlag("int_flag");
+
+  ASSERT_TRUE(flag_01);
+  EXPECT_EQ(flag_01->Name(), "int_flag");
+  EXPECT_EQ(flag_01->Help(), "int_flag help");
+  EXPECT_TRUE(!flag_01->IsRetired());
+  EXPECT_TRUE(flag_01->IsOfType<int>());
+  EXPECT_TRUE(!flag_01->IsOfType<bool>());
+  EXPECT_TRUE(!flag_01->IsOfType<std::string>());
+  EXPECT_TRUE(absl::EndsWith(flag_01->Filename(),
+                             "absl/flags/commandlineflag_test.cc"))
+      << flag_01->Filename();
+
+  auto* flag_02 = absl::FindCommandLineFlag("string_flag");
+
+  ASSERT_TRUE(flag_02);
+  EXPECT_EQ(flag_02->Name(), "string_flag");
+  EXPECT_EQ(flag_02->Help(), "string_flag help");
+  EXPECT_TRUE(!flag_02->IsRetired());
+  EXPECT_TRUE(flag_02->IsOfType<std::string>());
+  EXPECT_TRUE(!flag_02->IsOfType<bool>());
+  EXPECT_TRUE(!flag_02->IsOfType<int>());
+  EXPECT_TRUE(absl::EndsWith(flag_02->Filename(),
+                             "absl/flags/commandlineflag_test.cc"))
+      << flag_02->Filename();
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(CommandLineFlagTest, TestValueAccessMethods) {
+  absl::SetFlag(&FLAGS_int_flag2, 301);
+  auto* flag_01 = absl::FindCommandLineFlag("int_flag2");
+
+  ASSERT_TRUE(flag_01);
+  EXPECT_EQ(flag_01->CurrentValue(), "301");
+  EXPECT_EQ(flag_01->DefaultValue(), "201");
+
+  absl::SetFlag(&FLAGS_string_flag2, "new_str_value");
+  auto* flag_02 = absl::FindCommandLineFlag("string_flag2");
+
+  ASSERT_TRUE(flag_02);
+  EXPECT_EQ(flag_02->CurrentValue(), "new_str_value");
+  EXPECT_EQ(flag_02->DefaultValue(), "dflt");
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(CommandLineFlagTest, TestParseFromCurrentValue) {
+  std::string err;
+
+  auto* flag_01 = absl::FindCommandLineFlag("int_flag");
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "11", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 11);
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "-123", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "xyz", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
+  EXPECT_EQ(err, "Illegal value 'xyz' specified for flag 'int_flag'");
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "A1", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), -123);
+  EXPECT_EQ(err, "Illegal value 'A1' specified for flag 'int_flag'");
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "0x10", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 16);
+  EXPECT_FALSE(
+      flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "011", flags::SET_FLAGS_VALUE, flags::kCommandLine, err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 11);
+  EXPECT_TRUE(flags::PrivateHandleAccessor::IsSpecifiedOnCommandLine(*flag_01));
+
+  EXPECT_TRUE(!flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, err));
+  EXPECT_EQ(err, "Illegal value '' specified for flag 'int_flag'");
+
+  auto* flag_02 = absl::FindCommandLineFlag("string_flag");
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_02, "xyz", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_string_flag), "xyz");
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_02, "", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange, err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_string_flag), "");
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(CommandLineFlagTest, TestParseFromDefaultValue) {
+  std::string err;
+
+  auto* flag_01 = absl::FindCommandLineFlag("int_flag");
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "111", flags::SET_FLAGS_DEFAULT, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(flag_01->DefaultValue(), "111");
+
+  auto* flag_02 = absl::FindCommandLineFlag("string_flag");
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_02, "abc", flags::SET_FLAGS_DEFAULT, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(flag_02->DefaultValue(), "abc");
+}
+
+// --------------------------------------------------------------------
+
+TEST_F(CommandLineFlagTest, TestParseFromIfDefault) {
+  std::string err;
+
+  auto* flag_01 = absl::FindCommandLineFlag("int_flag");
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "22", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
+      err))
+      << err;
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 22);
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "33", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 22);
+  // EXPECT_EQ(err, "ERROR: int_flag is already set to 22");
+
+  // Reset back to default value
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "201", flags::SET_FLAGS_VALUE, flags::kProgrammaticChange,
+      err));
+
+  EXPECT_TRUE(flags::PrivateHandleAccessor::ParseFrom(
+      *flag_01, "33", flags::SET_FLAG_IF_DEFAULT, flags::kProgrammaticChange,
+      err));
+  EXPECT_EQ(absl::GetFlag(FLAGS_int_flag), 201);
+  // EXPECT_EQ(err, "ERROR: int_flag is already set to 201");
+}
+
+}  // namespace