1 files changed, 39 insertions, 0 deletions
diff --git a/libc/test/src/string/strcat_test.cpp b/libc/test/src/string/strcat_test.cpp
new file mode 100644
index 00000000000..3b8a7a7e447
--- /dev/null
+++ b/libc/test/src/string/strcat_test.cpp
@@ -0,0 +1,39 @@
+//===---------------------- Unittests for strcat --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <string>
+
+#include "src/string/strcat/strcat.h"
+#include "gtest/gtest.h"
+
+TEST(StrCatTest, EmptyDest) {
+  std::string abc = "abc";
+  char dest[4];
+
+  dest[0] = '\0';
+
+  char *result = __llvm_libc::strcat(dest, abc.c_str());
+  ASSERT_EQ(dest, result);
+  ASSERT_EQ(std::string(dest), abc);
+  ASSERT_EQ(std::string(dest).size(), abc.size());
+}
+
+TEST(StrCatTest, NonEmptyDest) {
+  std::string abc = "abc";
+  char dest[7];
+
+  dest[0] = 'x';
+  dest[1] = 'y';
+  dest[2] = 'z';
+  dest[3] = '\0';
+
+  char *result = __llvm_libc::strcat(dest, abc.c_str());
+  ASSERT_EQ(dest, result);
+  ASSERT_EQ(std::string(dest), std::string("xyz") + abc);
+  ASSERT_EQ(std::string(dest).size(), abc.size() + 3);
+}