diff --git a/tests/string_test.cpp b/tests/string_test.cpp
new file mode 100644
index 0000000..ea1491c
--- /dev/null
+++ b/tests/string_test.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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 <gtest/gtest.h>
+
+#include <errno.h>
+#include <string.h>
+
+TEST(string, strerror) {
+  // Valid.
+  ASSERT_STREQ("Success", strerror(0));
+  ASSERT_STREQ("Operation not permitted", strerror(1));
+
+  // Invalid.
+  ASSERT_STREQ("Unknown error 4294967295", strerror(-1));
+  ASSERT_STREQ("Unknown error 1234", strerror(1234));
+}
+
+void* ConcurrentStrErrorFn(void* arg) {
+  bool equal = (strcmp("Unknown error 2002", strerror(2002)) == 0);
+  return reinterpret_cast<void*>(equal);
+}
+
+#if __BIONIC__ // glibc's strerror isn't thread safe, only its strsignal.
+TEST(string, strerror_concurrent) {
+  const char* strerror1001 = strerror(1001);
+  ASSERT_STREQ("Unknown error 1001", strerror1001);
+
+  pthread_t t;
+  ASSERT_EQ(0, pthread_create(&t, NULL, ConcurrentStrErrorFn, NULL));
+  void* result;
+  ASSERT_EQ(0, pthread_join(t, &result));
+  ASSERT_TRUE(static_cast<bool>(result));
+
+  ASSERT_STREQ("Unknown error 1001", strerror1001);
+}
+#endif
+
+#if __BIONIC__ // glibc's strerror_r doesn't even have the same signature as the POSIX one.
+TEST(string, strerror_r) {
+  char buf[256];
+
+  // Valid.
+  ASSERT_EQ(0, strerror_r(0, buf, sizeof(buf)));
+  ASSERT_STREQ("Success", buf);
+  ASSERT_EQ(0, strerror_r(1, buf, sizeof(buf)));
+  ASSERT_STREQ("Operation not permitted", buf);
+
+  // Invalid.
+  ASSERT_EQ(0, strerror_r(-1, buf, sizeof(buf)));
+  ASSERT_STREQ("Unknown error 4294967295", buf);
+  ASSERT_EQ(0, strerror_r(1234, buf, sizeof(buf)));
+  ASSERT_STREQ("Unknown error 1234", buf);
+
+  // Buffer too small.
+  ASSERT_EQ(-1, strerror_r(0, buf, 2));
+  ASSERT_EQ(ERANGE, errno);
+}
+#endif
+
+TEST(string, strsignal) {
+  // A regular signal.
+  ASSERT_STREQ("Hangup", strsignal(1));
+
+  // A real-time signal.
+#ifdef __GLIBC__ // glibc reserves real-time signals for internal use, and doesn't count those.
+  ASSERT_STREQ("Real-time signal 14", strsignal(48));
+#else
+  ASSERT_STREQ("Real-time signal 16", strsignal(48));
+#endif
+
+  // Errors.
+  ASSERT_STREQ("Unknown signal -1", strsignal(-1)); // Too small.
+  ASSERT_STREQ("Unknown signal 0", strsignal(0)); // Still too small.
+  ASSERT_STREQ("Unknown signal 1234", strsignal(1234)); // Too large.
+}
+
+void* ConcurrentStrSignalFn(void* arg) {
+  bool equal = (strcmp("Unknown signal 2002", strsignal(2002)) == 0);
+  return reinterpret_cast<void*>(equal);
+}
+
+TEST(string, strsignal_concurrent) {
+  const char* strsignal1001 = strsignal(1001);
+  ASSERT_STREQ("Unknown signal 1001", strsignal1001);
+
+  pthread_t t;
+  ASSERT_EQ(0, pthread_create(&t, NULL, ConcurrentStrSignalFn, NULL));
+  void* result;
+  ASSERT_EQ(0, pthread_join(t, &result));
+  ASSERT_TRUE(static_cast<bool>(result));
+
+  ASSERT_STREQ("Unknown signal 1001", strsignal1001);
+}