diff --git a/clang/unittests/FileManager/FileManagerTest.cpp b/clang/unittests/FileManager/FileManagerTest.cpp
new file mode 100644
index 0000000..a7d3df3
--- /dev/null
+++ b/clang/unittests/FileManager/FileManagerTest.cpp
@@ -0,0 +1,222 @@
+//===- unittests/FileManager/FileMangerTest.cpp ------ FileManger tests ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Basic/FileSystemOptions.h"
+#include "clang/Basic/FileSystemStatCache.h"
+#include "clang/Basic/FileManager.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace clang;
+
+namespace {
+
+// Used to create a fake file system for running the tests with such
+// that the tests are not affected by the structure/contents of the
+// file system on the machine running the tests.
+class FakeStatCache : public FileSystemStatCache {
+private:
+  // Maps a file/directory path to its desired stat result.  Anything
+  // not in this map is considered to not exist in the file system.
+  llvm::StringMap<struct stat, llvm::BumpPtrAllocator> StatCalls;
+
+  void InjectFileOrDirectory(const char *Path, ino_t INode, bool IsFile) {
+    struct stat statBuf = {};
+    statBuf.st_dev = 1;
+#ifndef LLVM_ON_WIN32  // struct stat has no st_ino field on Windows.
+    statBuf.st_ino = INode;
+#endif
+    statBuf.st_mode = IsFile ? (0777 | S_IFREG)  // a regular file
+        : (0777 | S_IFDIR);  // a directory
+    StatCalls[Path] = statBuf;
+  }
+
+public:
+  // Inject a file with the given inode value to the fake file system.
+  void InjectFile(const char *Path, ino_t INode) {
+    InjectFileOrDirectory(Path, INode, /*IsFile=*/true);
+  }
+
+  // Inject a directory with the given inode value to the fake file system.
+  void InjectDirectory(const char *Path, ino_t INode) {
+    InjectFileOrDirectory(Path, INode, /*IsFile=*/false);
+  }
+
+  // Implement FileSystemStatCache::getStat().
+  virtual LookupResult getStat(const char *Path, struct stat &StatBuf,
+                               int *FileDescriptor) {
+    if (StatCalls.count(Path) != 0) {
+      StatBuf = StatCalls[Path];
+      return CacheExists;
+    }
+
+    return CacheMissing;  // This means the file/directory doesn't exist.
+  }
+};
+
+// The test fixture.
+class FileManagerTest : public ::testing::Test {
+ protected:
+  FileManagerTest() : manager(options) {
+  }
+
+  FileSystemOptions options;
+  FileManager manager;
+};
+
+// When a virtual file is added, its getDir() field is set correctly
+// (not NULL, correct name).
+TEST_F(FileManagerTest, getVirtualFileSetsTheDirFieldCorrectly) {
+  const FileEntry *file = manager.getVirtualFile("foo.cpp", 42, 0);
+  ASSERT_TRUE(file != NULL);
+
+  const DirectoryEntry *dir = file->getDir();
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ(".", dir->getName());
+
+  file = manager.getVirtualFile("x/y/z.cpp", 42, 0);
+  ASSERT_TRUE(file != NULL);
+
+  dir = file->getDir();
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ("x/y", dir->getName());
+}
+
+// Before any virtual file is added, no virtual directory exists.
+TEST_F(FileManagerTest, NoVirtualDirectoryExistsBeforeAVirtualFileIsAdded) {
+  // An empty FakeStatCache causes all stat calls made by the
+  // FileManager to report "file/directory doesn't exist".  This
+  // avoids the possibility of the result of this test being affected
+  // by what's in the real file system.
+  manager.addStatCache(new FakeStatCache);
+
+  EXPECT_EQ(NULL, manager.getDirectory("virtual/dir/foo"));
+  EXPECT_EQ(NULL, manager.getDirectory("virtual/dir"));
+  EXPECT_EQ(NULL, manager.getDirectory("virtual"));
+}
+
+// When a virtual file is added, all of its ancestors should be created.
+TEST_F(FileManagerTest, getVirtualFileCreatesDirectoryEntriesForAncestors) {
+  // Fake an empty real file system.
+  manager.addStatCache(new FakeStatCache);
+
+  manager.getVirtualFile("virtual/dir/bar.h", 100, 0);
+  EXPECT_EQ(NULL, manager.getDirectory("virtual/dir/foo"));
+
+  const DirectoryEntry *dir = manager.getDirectory("virtual/dir");
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ("virtual/dir", dir->getName());
+
+  dir = manager.getDirectory("virtual");
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ("virtual", dir->getName());
+}
+
+// getFile() returns non-NULL if a real file exists at the given path.
+TEST_F(FileManagerTest, getFileReturnsValidFileEntryForExistingRealFile) {
+  // Inject fake files into the file system.
+  FakeStatCache *statCache = new FakeStatCache;
+  statCache->InjectDirectory("/tmp", 42);
+  statCache->InjectFile("/tmp/test", 43);
+  manager.addStatCache(statCache);
+
+  const FileEntry *file = manager.getFile("/tmp/test");
+  ASSERT_TRUE(file != NULL);
+  EXPECT_STREQ("/tmp/test", file->getName());
+
+  const DirectoryEntry *dir = file->getDir();
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ("/tmp", dir->getName());
+}
+
+// getFile() returns non-NULL if a virtual file exists at the given path.
+TEST_F(FileManagerTest, getFileReturnsValidFileEntryForExistingVirtualFile) {
+  // Fake an empty real file system.
+  manager.addStatCache(new FakeStatCache);
+
+  manager.getVirtualFile("virtual/dir/bar.h", 100, 0);
+  const FileEntry *file = manager.getFile("virtual/dir/bar.h");
+  ASSERT_TRUE(file != NULL);
+  EXPECT_STREQ("virtual/dir/bar.h", file->getName());
+
+  const DirectoryEntry *dir = file->getDir();
+  ASSERT_TRUE(dir != NULL);
+  EXPECT_STREQ("virtual/dir", dir->getName());
+}
+
+// getFile() returns different FileEntries for different paths when
+// there's no aliasing.
+TEST_F(FileManagerTest, getFileReturnsDifferentFileEntriesForDifferentFiles) {
+  // Inject two fake files into the file system.  Different inodes
+  // mean the files are not symlinked together.
+  FakeStatCache *statCache = new FakeStatCache;
+  statCache->InjectDirectory(".", 41);
+  statCache->InjectFile("foo.cpp", 42);
+  statCache->InjectFile("bar.cpp", 43);
+  manager.addStatCache(statCache);
+
+  const FileEntry *fileFoo = manager.getFile("foo.cpp");
+  const FileEntry *fileBar = manager.getFile("bar.cpp");
+  ASSERT_TRUE(fileFoo != NULL);
+  ASSERT_TRUE(fileBar != NULL);
+  EXPECT_NE(fileFoo, fileBar);
+}
+
+// getFile() returns NULL if neither a real file nor a virtual file
+// exists at the given path.
+TEST_F(FileManagerTest, getFileReturnsNULLForNonexistentFile) {
+  // Inject a fake foo.cpp into the file system.
+  FakeStatCache *statCache = new FakeStatCache;
+  statCache->InjectDirectory(".", 41);
+  statCache->InjectFile("foo.cpp", 42);
+  manager.addStatCache(statCache);
+
+  // Create a virtual bar.cpp file.
+  manager.getVirtualFile("bar.cpp", 200, 0);
+
+  const FileEntry *file = manager.getFile("xyz.txt");
+  EXPECT_EQ(NULL, file);
+}
+
+// The following tests apply to Unix-like system only.
+
+#ifndef LLVM_ON_WIN32
+
+// getFile() returns the same FileEntry for real files that are aliases.
+TEST_F(FileManagerTest, getFileReturnsSameFileEntryForAliasedRealFiles) {
+  // Inject two real files with the same inode.
+  FakeStatCache *statCache = new FakeStatCache;
+  statCache->InjectDirectory("abc", 41);
+  statCache->InjectFile("abc/foo.cpp", 42);
+  statCache->InjectFile("abc/bar.cpp", 42);
+  manager.addStatCache(statCache);
+
+  EXPECT_EQ(manager.getFile("abc/foo.cpp"), manager.getFile("abc/bar.cpp"));
+}
+
+// getFile() returns the same FileEntry for virtual files that have
+// corresponding real files that are aliases.
+TEST_F(FileManagerTest, getFileReturnsSameFileEntryForAliasedVirtualFiles) {
+  // Inject two real files with the same inode.
+  FakeStatCache *statCache = new FakeStatCache;
+  statCache->InjectDirectory("abc", 41);
+  statCache->InjectFile("abc/foo.cpp", 42);
+  statCache->InjectFile("abc/bar.cpp", 42);
+  manager.addStatCache(statCache);
+
+  manager.getVirtualFile("abc/foo.cpp", 100, 0);
+  manager.getVirtualFile("abc/bar.cpp", 200, 0);
+
+  EXPECT_EQ(manager.getFile("abc/foo.cpp"), manager.getFile("abc/bar.cpp"));
+}
+
+#endif  // !LLVM_ON_WIN32
+
+} // anonymous namespace