diff --git a/starboard/nplb/BUILD.gn b/starboard/nplb/BUILD.gn
index 6f8577fe4af8..9e42544a8a68 100644
--- a/starboard/nplb/BUILD.gn
+++ b/starboard/nplb/BUILD.gn
@@ -135,6 +135,10 @@ target(gtest_target_type, "nplb") {
     "player_test_util.cc",
     "player_test_util.h",
     "player_write_sample_test.cc",
+    "posix_compliance/posix_string_compare_no_case_n_test.cc",
+    "posix_compliance/posix_string_compare_no_case_test.cc",
+    "posix_compliance/posix_string_format_test.cc",
+    "posix_compliance/posix_string_format_wide_test.cc",
     "random_helpers.cc",
     "recursive_mutex_test.cc",
     "rwlock_test.cc",
diff --git a/starboard/nplb/posix_compliance/posix_string_compare_no_case_n_test.cc b/starboard/nplb/posix_compliance/posix_string_compare_no_case_n_test.cc
new file mode 100644
index 000000000000..6b98cb4c6c40
--- /dev/null
+++ b/starboard/nplb/posix_compliance/posix_string_compare_no_case_n_test.cc
@@ -0,0 +1,61 @@
+// Copyright 2015 The Cobalt Authors. All Rights Reserved.
+//
+// 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
+//
+//     http://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 "starboard/common/string.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace starboard {
+namespace nplb {
+namespace {
+
+#if SB_API_VERSION >= 16
+TEST(PosixCompareNoCaseNTest, SunnyDaySelf) {
+  const char kString[] = "0123456789";
+  EXPECT_EQ(0, strncasecmp(kString, kString, strlen(kString)));
+  EXPECT_EQ(0, strncasecmp("", "", 0));
+}
+
+TEST(PosixCompareNoCaseNTest, SunnyDayEmptyLessThanNotEmpty) {
+  const char kString[] = "0123456789";
+  EXPECT_GT(0, strncasecmp("", kString, strlen(kString)));
+}
+
+TEST(PosixCompareNoCaseNTest, SunnyDayEmptyZeroNEqual) {
+  const char kString[] = "0123456789";
+  EXPECT_EQ(0, strncasecmp("", kString, 0));
+}
+
+TEST(PosixCompareNoCaseNTest, SunnyDayBigN) {
+  const char kString[] = "0123456789";
+  EXPECT_EQ(0, strncasecmp(kString, kString, strlen(kString) * 2));
+}
+
+TEST(PosixCompareNoCaseNTest, SunnyDayCase) {
+  const char kString1[] = "aBcDeFgHiJkLmNoPqRsTuVwXyZ";
+  const char kString2[] = "AbCdEfGhIjKlMnOpQrStUvWxYz";
+  EXPECT_EQ(0, strncasecmp(kString1, kString2, strlen(kString1)));
+  EXPECT_EQ(0, strncasecmp(kString2, kString1, strlen(kString2)));
+
+  const char kString3[] = "aBcDeFgHiJkLmaBcDeFgHiJkLm";
+  const char kString4[] = "AbCdEfGhIjKlMnOpQrStUvWxYz";
+  EXPECT_GT(0, strncasecmp(kString3, kString4, strlen(kString3)));
+  EXPECT_LT(0, strncasecmp(kString4, kString3, strlen(kString4)));
+  EXPECT_EQ(0, strncasecmp(kString3, kString4, strlen(kString3) / 2));
+  EXPECT_EQ(0, strncasecmp(kString4, kString3, strlen(kString4) / 2));
+}
+#endif  // SB_API_VERSION >= 16
+
+}  // namespace
+}  // namespace nplb
+}  // namespace starboard
diff --git a/starboard/nplb/posix_compliance/posix_string_compare_no_case_test.cc b/starboard/nplb/posix_compliance/posix_string_compare_no_case_test.cc
new file mode 100644
index 000000000000..1417a10bf693
--- /dev/null
+++ b/starboard/nplb/posix_compliance/posix_string_compare_no_case_test.cc
@@ -0,0 +1,43 @@
+// Copyright 2015 The Cobalt Authors. All Rights Reserved.
+//
+// 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
+//
+//     http://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 "starboard/common/string.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace starboard {
+namespace nplb {
+namespace {
+
+#if SB_API_VERSION >= 16
+TEST(PosixCompareNoCaseTest, SunnyDaySelf) {
+  const char kString[] = "0123456789";
+  EXPECT_EQ(0, strcasecmp(kString, kString));
+  EXPECT_EQ(0, strcasecmp("", ""));
+}
+
+TEST(PosixCompareNoCaseTest, SunnyDayEmptyLessThanNotEmpty) {
+  const char kString[] = "0123456789";
+  EXPECT_GT(0, strcasecmp("", kString));
+}
+
+TEST(PosixCompareNoCaseTest, SunnyDayCase) {
+  const char kString1[] = "aBcDeFgHiJkLmNoPqRsTuVwXyZ";
+  const char kString2[] = "AbCdEfGhIjKlMnOpQrStUvWxYz";
+  EXPECT_EQ(0, strcasecmp(kString1, kString2));
+  EXPECT_EQ(0, strcasecmp(kString2, kString1));
+}
+#endif  // SB_API_VERSION >= 16
+}  // namespace
+}  // namespace nplb
+}  // namespace starboard
diff --git a/starboard/nplb/posix_compliance/posix_string_format_test.cc b/starboard/nplb/posix_compliance/posix_string_format_test.cc
new file mode 100644
index 000000000000..e1a793dc15c9
--- /dev/null
+++ b/starboard/nplb/posix_compliance/posix_string_format_test.cc
@@ -0,0 +1,50 @@
+// Copyright 2015 The Cobalt Authors. All Rights Reserved.
+//
+// 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
+//
+//     http://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.
+
+// Here we are not trying to do anything fancy, just to really sanity check that
+// this is hooked up to something.
+#if SB_API_VERSION >= 16
+
+#include "starboard/common/string.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace starboard {
+namespace nplb {
+namespace {
+
+int Format(char* out_buffer, size_t buffer_size, const char* format, ...) {
+  va_list arguments;
+  va_start(arguments, format);
+  int result = vsnprintf(out_buffer, buffer_size, format, arguments);
+  va_end(arguments);
+  return result;
+}
+
+TEST(PosixFormatTest, SunnyDay) {
+  const char kExpected[] = "a1b2c3test";
+  char destination[1024] = {0};
+  int result = Format(destination, SB_ARRAY_SIZE(destination), "a%db%dc%d%s", 1,
+                      2, 3, "test");
+  size_t expected_length = strlen(kExpected);
+  EXPECT_EQ(expected_length, result);
+  for (size_t i = 0; i <= expected_length; ++i) {
+    EXPECT_EQ(kExpected[i], destination[i]);
+  }
+}
+
+}  // namespace
+}  // namespace nplb
+}  // namespace starboard
+   //
+#endif  // SB_API_VERSION >= 16
diff --git a/starboard/nplb/posix_compliance/posix_string_format_wide_test.cc b/starboard/nplb/posix_compliance/posix_string_format_wide_test.cc
new file mode 100644
index 000000000000..1a6e39defc38
--- /dev/null
+++ b/starboard/nplb/posix_compliance/posix_string_format_wide_test.cc
@@ -0,0 +1,53 @@
+// Copyright 2015 The Cobalt Authors. All Rights Reserved.
+//
+// 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
+//
+//     http://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.
+
+// Here we are not trying to do anything fancy, just to really sanity check that
+// this is hooked up to something.
+#if SB_API_VERSION >= 16
+
+#include "starboard/common/string.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace starboard {
+namespace nplb {
+namespace {
+
+int Format(wchar_t* out_buffer,
+           size_t buffer_size,
+           const wchar_t* format,
+           ...) {
+  va_list arguments;
+  va_start(arguments, format);
+  int result = vswprintf(out_buffer, buffer_size, format, arguments);
+  va_end(arguments);
+  return result;
+}
+
+TEST(PosixFormatWideTest, SunnyDay) {
+  const wchar_t kExpected[] = L"a1b2c3test";
+  wchar_t destination[1024] = {0};
+  int result = Format(destination, SB_ARRAY_SIZE(destination), L"a%db%dc%d%s",
+                      1, 2, 3, "test");
+  size_t expected_length = wcslen(kExpected);
+  EXPECT_EQ(expected_length, result);
+  for (size_t i = 0; i <= expected_length; ++i) {
+    EXPECT_EQ(kExpected[i], destination[i]);
+  }
+}
+
+}  // namespace
+}  // namespace nplb
+}  // namespace starboard
+
+#endif  // SB_API_VERSION >= 16