diff --git a/src/commandlineflags.cc b/src/commandlineflags.cc
index 734e88bb..6bd65c5a 100644
--- a/src/commandlineflags.cc
+++ b/src/commandlineflags.cc
@@ -21,6 +21,8 @@
 #include <limits>
 
 namespace benchmark {
+namespace {
+
 // Parses 'str' for a 32-bit signed integer.  If successful, writes
 // the result to *value and returns true; otherwise leaves *value
 // unchanged and returns false.
@@ -88,6 +90,8 @@ static std::string FlagToEnvVar(const char* flag) {
   return "BENCHMARK_" + env_var;
 }
 
+}  // namespace
+
 // Reads and returns the Boolean environment variable corresponding to
 // the given flag; if it's not set, returns default_value.
 //
diff --git a/src/commandlineflags.h b/src/commandlineflags.h
index 945c9a9f..5eaea82a 100644
--- a/src/commandlineflags.h
+++ b/src/commandlineflags.h
@@ -23,16 +23,10 @@
   std::string FLAG(name) = (default_val)
 
 namespace benchmark {
-// Parses 'str' for a 32-bit signed integer.  If successful, writes the result
-// to *value and returns true; otherwise leaves *value unchanged and returns
-// false.
-bool ParseInt32(const std::string& src_text, const char* str, int32_t* value);
-
 // Parses a bool/Int32/string from the environment variable
 // corresponding to the given Google Test flag.
 bool BoolFromEnv(const char* flag, bool default_val);
 int32_t Int32FromEnv(const char* flag, int32_t default_val);
-double DoubleFromEnv(const char* flag, double default_val);
 const char* StringFromEnv(const char* flag, const char* default_val);
 
 // Parses a string for a bool flag, in the form of either
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 62370a54..d3a07639 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -195,6 +195,7 @@ if (BENCHMARK_ENABLE_GTEST_TESTS)
 
   add_gtest(benchmark_gtest)
   add_gtest(benchmark_name_gtest)
+  add_gtest(commandlineflags_gtest)
   add_gtest(statistics_gtest)
   add_gtest(string_util_gtest)
 endif(BENCHMARK_ENABLE_GTEST_TESTS)
diff --git a/test/commandlineflags_gtest.cc b/test/commandlineflags_gtest.cc
new file mode 100644
index 00000000..5460778c
--- /dev/null
+++ b/test/commandlineflags_gtest.cc
@@ -0,0 +1,78 @@
+#include <cstdlib>
+
+#include "../src/commandlineflags.h"
+#include "../src/internal_macros.h"
+#include "gtest/gtest.h"
+
+namespace benchmark {
+namespace {
+
+#if defined(BENCHMARK_OS_WINDOWS)
+int setenv(const char* name, const char* value, int overwrite) {
+  if (!overwrite) {
+    // NOTE: getenv_s is far superior but not available under mingw.
+    char* env_value = getenv(name);
+    if (env_value == nullptr) {
+      return -1;
+    }
+  }
+  return _putenv_s(name, value);
+}
+
+int unsetenv(const char* name) {
+  return _putenv_s(name, "");
+}
+
+#endif  // BENCHMARK_OS_WINDOWS
+
+TEST(BoolFromEnv, Default) {
+  ASSERT_EQ(unsetenv("BENCHMARK_NOT_IN_ENV"), 0);
+  EXPECT_EQ(BoolFromEnv("not_in_env", true), true);
+}
+
+TEST(BoolFromEnv, False) {
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "0", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", true), false);
+  unsetenv("BENCHMARK_IN_ENV");
+}
+
+TEST(BoolFromEnv, True) {
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "1", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("BENCHMARK_IN_ENV");
+
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "foo", 1), 0);
+  EXPECT_EQ(BoolFromEnv("in_env", false), true);
+  unsetenv("BENCHMARK_IN_ENV");
+}
+
+TEST(Int32FromEnv, NotInEnv) {
+  ASSERT_EQ(unsetenv("BENCHMARK_NOT_IN_ENV"), 0);
+  EXPECT_EQ(Int32FromEnv("not_in_env", 42), 42);
+}
+
+TEST(Int32FromEnv, InvalidInteger) {
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "foo", 1), 0);
+  EXPECT_EQ(Int32FromEnv("in_env", 42), 42);
+  ASSERT_EQ(unsetenv("BENCHMARK_IN_ENV"), 0);
+}
+
+TEST(Int32FromEnv, ValidInteger) {
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "42", 1), 0);
+  EXPECT_EQ(Int32FromEnv("in_env", 64), 42);
+  unsetenv("BENCHMARK_IN_ENV");
+}
+
+TEST(StringFromEnv, Default) {
+  ASSERT_EQ(unsetenv("BENCHMARK_NOT_IN_ENV"), 0);
+  EXPECT_STREQ(StringFromEnv("not_in_env", "foo"), "foo");
+}
+
+TEST(StringFromEnv, Valid) {
+  ASSERT_EQ(setenv("BENCHMARK_IN_ENV", "foo", 1), 0);
+  EXPECT_STREQ(StringFromEnv("in_env", "bar"), "foo");
+  unsetenv("BENCHMARK_IN_ENV");
+}
+
+}  // namespace
+}  // namespace benchmark