diff --git a/llvm/unittests/Support/TarWriterTest.cpp b/llvm/unittests/Support/TarWriterTest.cpp
new file mode 100644
index 0000000..dfcf88f
--- /dev/null
+++ b/llvm/unittests/Support/TarWriterTest.cpp
@@ -0,0 +1,88 @@
+//===- llvm/unittest/Support/TarWriterTest.cpp ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/TarWriter.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+namespace {
+
+struct UstarHeader {
+  char Name[100];
+  char Mode[8];
+  char Uid[8];
+  char Gid[8];
+  char Size[12];
+  char Mtime[12];
+  char Checksum[8];
+  char TypeFlag;
+  char Linkname[100];
+  char Magic[6];
+  char Version[2];
+  char Uname[32];
+  char Gname[32];
+  char DevMajor[8];
+  char DevMinor[8];
+  char Prefix[155];
+  char Pad[12];
+};
+
+class TarWriterTest : public ::testing::Test {};
+
+static UstarHeader create(StringRef Base, StringRef Filename) {
+  // Create a temporary file.
+  SmallString<128> Path;
+  std::error_code EC =
+      sys::fs::createTemporaryFile("TarWriterTest", "tar", Path);
+  EXPECT_FALSE((bool)EC);
+
+  // Create a tar file.
+  Expected<std::unique_ptr<TarWriter>> TarOrErr = TarWriter::create(Path, Base);
+  EXPECT_TRUE((bool)TarOrErr);
+  std::unique_ptr<TarWriter> Tar = std::move(*TarOrErr);
+  Tar->append(Filename, "contents");
+  Tar.release();
+
+  // Read the tar file.
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = MemoryBuffer::getFile(Path);
+  EXPECT_TRUE((bool)MBOrErr);
+  std::unique_ptr<MemoryBuffer> MB = std::move(*MBOrErr);
+  sys::fs::remove(Path);
+  return *reinterpret_cast<const UstarHeader *>(MB->getBufferStart());
+}
+
+TEST_F(TarWriterTest, Basics) {
+  UstarHeader Hdr = create("base", "file");
+  ASSERT_EQ("ustar", StringRef(Hdr.Magic));
+  ASSERT_EQ("00", StringRef(Hdr.Version, 2));
+  ASSERT_EQ("base/file", StringRef(Hdr.Name));
+  ASSERT_EQ("00000000010", StringRef(Hdr.Size));
+}
+
+TEST_F(TarWriterTest, LongFilename) {
+  UstarHeader Hdr1 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(44, 'x') + "/foo");
+  ASSERT_EQ("foo", StringRef(Hdr1.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x') + "/" + std::string(44, 'x'),
+            StringRef(Hdr1.Prefix));
+
+  UstarHeader Hdr2 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(45, 'x') + "/foo");
+  ASSERT_EQ("foo", StringRef(Hdr2.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x') + "/" + std::string(45, 'x'),
+            StringRef(Hdr2.Prefix));
+
+  UstarHeader Hdr3 = create(
+      "012345678", std::string(99, 'x') + "/" + std::string(46, 'x') + "/foo");
+  ASSERT_EQ(std::string(46, 'x') + "/foo", StringRef(Hdr3.Name));
+  ASSERT_EQ("012345678/" + std::string(99, 'x'), StringRef(Hdr3.Prefix));
+}
+}