diff --git a/build/VStudio/testing/winfsp-tests.vcxproj b/build/VStudio/testing/winfsp-tests.vcxproj
index 36c2114d..98fcfd3b 100644
--- a/build/VStudio/testing/winfsp-tests.vcxproj
+++ b/build/VStudio/testing/winfsp-tests.vcxproj
@@ -184,6 +184,7 @@
     <ClCompile Include="..\..\..\tst\winfsp-tests\dirctl-test.c" />
     <ClCompile Include="..\..\..\tst\winfsp-tests\flush-test.c" />
     <ClCompile Include="..\..\..\tst\winfsp-tests\info-test.c" />
+    <ClCompile Include="..\..\..\tst\winfsp-tests\lock-test.c" />
     <ClCompile Include="..\..\..\tst\winfsp-tests\memfs-test.c" />
     <ClCompile Include="..\..\..\tst\winfsp-tests\memfs.cpp" />
     <ClCompile Include="..\..\..\tst\winfsp-tests\mount-test.c" />
diff --git a/build/VStudio/testing/winfsp-tests.vcxproj.filters b/build/VStudio/testing/winfsp-tests.vcxproj.filters
index 3523d99f..417227fc 100644
--- a/build/VStudio/testing/winfsp-tests.vcxproj.filters
+++ b/build/VStudio/testing/winfsp-tests.vcxproj.filters
@@ -49,6 +49,9 @@
     <ClCompile Include="..\..\..\tst\winfsp-tests\flush-test.c">
       <Filter>Source</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\tst\winfsp-tests\lock-test.c">
+      <Filter>Source</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\..\..\ext\tlib\testsuite.h">
diff --git a/tst/winfsp-tests/lock-test.c b/tst/winfsp-tests/lock-test.c
new file mode 100644
index 00000000..7126ebb2
--- /dev/null
+++ b/tst/winfsp-tests/lock-test.c
@@ -0,0 +1,542 @@
+#include <winfsp/winfsp.h>
+#include <tlib/testsuite.h>
+#include <strsafe.h>
+#include <time.h>
+#include <VersionHelpers.h>
+#include "memfs.h"
+
+void *memfs_start_ex(ULONG Flags, ULONG FileInfoTimeout);
+void *memfs_start(ULONG Flags);
+void memfs_stop(void *data);
+PWSTR memfs_volumename(void *data);
+
+extern int NtfsTests;
+extern int WinFspDiskTests;
+extern int WinFspNetTests;
+
+static void lock_dotest(ULONG Flags, PWSTR VolPrefix, PWSTR Prefix, ULONG FileInfoTimeout, DWORD CreateFlags)
+{
+    /* this is not a true locking test since you need 2 processes to really test locks */
+
+    void *memfs = memfs_start_ex(Flags, FileInfoTimeout);
+
+    HANDLE Handle;
+    BOOL Success;
+    WCHAR FilePath[MAX_PATH];
+    SYSTEM_INFO SystemInfo;
+    DWORD SectorsPerCluster;
+    DWORD BytesPerSector;
+    DWORD FreeClusters;
+    DWORD TotalClusters;
+    PVOID AllocBuffer[2], Buffer[2];
+    ULONG AllocBufferSize;
+    DWORD BytesTransferred;
+    DWORD FilePointer;
+
+    GetSystemInfo(&SystemInfo);
+
+    StringCbPrintfW(FilePath, sizeof FilePath, L"%s%s\\",
+        VolPrefix ? L"" : L"\\\\?\\GLOBALROOT", VolPrefix ? VolPrefix : memfs_volumename(memfs));
+
+    Success = GetDiskFreeSpaceW(FilePath, &SectorsPerCluster, &BytesPerSector, &FreeClusters, &TotalClusters);
+    ASSERT(Success);
+    AllocBufferSize = 16 * SystemInfo.dwPageSize;
+
+    AllocBuffer[0] = _aligned_malloc(AllocBufferSize, SystemInfo.dwPageSize);
+    AllocBuffer[1] = _aligned_malloc(AllocBufferSize, SystemInfo.dwPageSize);
+    ASSERT(0 != AllocBuffer[0] && 0 != AllocBuffer[1]);
+
+    srand((unsigned)time(0));
+    for (PUINT8 Bgn = AllocBuffer[0], End = Bgn + AllocBufferSize; End > Bgn; Bgn++)
+        *Bgn = rand();
+
+    Buffer[0] = (PVOID)((PUINT8)AllocBuffer[0] + BytesPerSector);
+    Buffer[1] = (PVOID)((PUINT8)AllocBuffer[1] + BytesPerSector);
+
+    StringCbPrintfW(FilePath, sizeof FilePath, L"%s%s\\file0",
+        Prefix ? L"" : L"\\\\?\\GLOBALROOT", Prefix ? Prefix : memfs_volumename(memfs));
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        CREATE_NEW, FILE_ATTRIBUTE_NORMAL | CreateFlags, 0);
+    ASSERT(INVALID_HANDLE_VALUE != Handle);
+
+    Success = LockFile(Handle, BytesPerSector / 2, 0, BytesPerSector, 0);
+    ASSERT(Success);
+
+    Success = LockFile(Handle, BytesPerSector + BytesPerSector / 2, 0, BytesPerSector, 0);
+    ASSERT(Success);
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    Success = WriteFile(Handle, Buffer[0], BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+
+    FilePointer = SetFilePointer(Handle, 2 * BytesPerSector, 0, FILE_BEGIN);
+    ASSERT(2 * BytesPerSector == FilePointer);
+    Success = WriteFile(Handle, Buffer[0], BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    FilePointer = SetFilePointer(Handle, 2 * BytesPerSector, 0, FILE_BEGIN);
+    ASSERT(2 * BytesPerSector == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    FilePointer = SetFilePointer(Handle, 2 * BytesPerSector, 0, FILE_BEGIN);
+    ASSERT(2 * BytesPerSector == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    FilePointer = SetFilePointer(Handle, 3 * BytesPerSector, 0, FILE_BEGIN);
+    ASSERT(3 * BytesPerSector == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(0 == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Buffer[0] = AllocBuffer[0];
+    Buffer[1] = AllocBuffer[0];
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Success = UnlockFile(Handle, 0, 0, BytesPerSector, 0);
+    ASSERT(!Success && ERROR_NOT_LOCKED == GetLastError());
+
+    Success = UnlockFile(Handle, BytesPerSector / 2, 0, BytesPerSector, 0);
+    ASSERT(Success);
+
+    Success = CloseHandle(Handle);
+    ASSERT(Success);
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | CreateFlags | FILE_FLAG_DELETE_ON_CLOSE, 0);
+    ASSERT(INVALID_HANDLE_VALUE != Handle);
+
+    FilePointer = SetFilePointer(Handle, 0, 0, FILE_BEGIN);
+    ASSERT(0 == FilePointer);
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, 0);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+    ASSERT(FilePointer + BytesTransferred == SetFilePointer(Handle, 0, 0, FILE_CURRENT));
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Success = CloseHandle(Handle);
+    ASSERT(Success);
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        OPEN_EXISTING, 0, 0);
+    ASSERT(INVALID_HANDLE_VALUE == Handle);
+    ASSERT(ERROR_FILE_NOT_FOUND == GetLastError());
+
+    _aligned_free(AllocBuffer[0]);
+    _aligned_free(AllocBuffer[1]);
+
+    memfs_stop(memfs);
+}
+
+static void lock_overlapped_dotest(ULONG Flags, PWSTR VolPrefix, PWSTR Prefix, ULONG FileInfoTimeout, DWORD CreateFlags)
+{
+    /* this is not a true locking test since you need 2 processes to really test locks */
+
+    void *memfs = memfs_start_ex(Flags, FileInfoTimeout);
+
+    HANDLE Handle;
+    BOOL Success;
+    WCHAR FilePath[MAX_PATH];
+    SYSTEM_INFO SystemInfo;
+    DWORD SectorsPerCluster;
+    DWORD BytesPerSector;
+    DWORD FreeClusters;
+    DWORD TotalClusters;
+    PVOID AllocBuffer[2], Buffer[2];
+    ULONG AllocBufferSize;
+    DWORD BytesTransferred;
+    OVERLAPPED Overlapped;
+
+    GetSystemInfo(&SystemInfo);
+
+    StringCbPrintfW(FilePath, sizeof FilePath, L"%s%s\\",
+        VolPrefix ? L"" : L"\\\\?\\GLOBALROOT", VolPrefix ? VolPrefix : memfs_volumename(memfs));
+
+    Success = GetDiskFreeSpaceW(FilePath, &SectorsPerCluster, &BytesPerSector, &FreeClusters, &TotalClusters);
+    ASSERT(Success);
+    AllocBufferSize = 16 * SystemInfo.dwPageSize;
+
+    AllocBuffer[0] = _aligned_malloc(AllocBufferSize, SystemInfo.dwPageSize);
+    AllocBuffer[1] = _aligned_malloc(AllocBufferSize, SystemInfo.dwPageSize);
+    ASSERT(0 != AllocBuffer[0] && 0 != AllocBuffer[1]);
+
+    srand((unsigned)time(0));
+    for (PUINT8 Bgn = AllocBuffer[0], End = Bgn + AllocBufferSize; End > Bgn; Bgn++)
+        *Bgn = rand();
+
+    Buffer[0] = (PVOID)((PUINT8)AllocBuffer[0] + BytesPerSector);
+    Buffer[1] = (PVOID)((PUINT8)AllocBuffer[1] + BytesPerSector);
+
+    StringCbPrintfW(FilePath, sizeof FilePath, L"%s%s\\file0",
+        Prefix ? L"" : L"\\\\?\\GLOBALROOT", Prefix ? Prefix : memfs_volumename(memfs));
+
+    memset(&Overlapped, 0, sizeof Overlapped);
+    Overlapped.hEvent = CreateEvent(0, TRUE, FALSE, 0);
+    ASSERT(0 != Overlapped.hEvent);
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        CREATE_NEW,
+        FILE_ATTRIBUTE_NORMAL | CreateFlags | FILE_FLAG_OVERLAPPED,
+        0);
+    ASSERT(INVALID_HANDLE_VALUE != Handle);
+
+    Overlapped.Offset = BytesPerSector / 2;
+    Success = LockFileEx(Handle, 0, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+
+    Overlapped.Offset = BytesPerSector + BytesPerSector / 2;
+    Success = LockFileEx(Handle, 0 | LOCKFILE_FAIL_IMMEDIATELY, 0,
+        BytesPerSector, 0, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+
+    Overlapped.Offset = BytesPerSector + BytesPerSector / 2;
+    Success = LockFileEx(Handle, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0,
+        BytesPerSector, 0, &Overlapped);
+    ASSERT(!Success && ERROR_LOCK_VIOLATION == GetLastError());
+
+    Overlapped.Offset = 0;
+    Success = WriteFile(Handle, Buffer[0], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError() || ERROR_LOCK_VIOLATION == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(!Success && ERROR_LOCK_VIOLATION == GetLastError());
+
+    Overlapped.Offset = BytesPerSector / 2;
+    Success = UnlockFileEx(Handle, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(Success);
+
+    Overlapped.Offset = BytesPerSector + BytesPerSector / 2;
+    Success = UnlockFileEx(Handle, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(Success);
+
+    Overlapped.Offset = BytesPerSector / 2;
+    Success = LockFileEx(Handle, LOCKFILE_EXCLUSIVE_LOCK, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+
+    Overlapped.Offset = BytesPerSector + BytesPerSector / 2;
+    Success = LockFileEx(Handle, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0,
+        BytesPerSector, 0, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+
+    Overlapped.Offset = 0;
+    Success = WriteFile(Handle, Buffer[0], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+
+    Overlapped.Offset = 2 * BytesPerSector;
+    Success = WriteFile(Handle, Buffer[0], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+
+    Overlapped.Offset = 0;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 2 * BytesPerSector;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 2 * BytesPerSector;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(BytesPerSector == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 3 * BytesPerSector;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError() || ERROR_HANDLE_EOF == GetLastError());
+    if (ERROR_HANDLE_EOF != GetLastError())
+    {
+        Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+        ASSERT(!Success && ERROR_HANDLE_EOF == GetLastError());
+    }
+    ASSERT(0 == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 0;
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+
+    Overlapped.Offset = 0;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Buffer[0] = AllocBuffer[0];
+    Buffer[1] = AllocBuffer[0];
+
+    Overlapped.Offset = 0;
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+
+    Overlapped.Offset = 0;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 0;
+    Success = WriteFile(Handle, Buffer[0], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+
+    Overlapped.Offset = 0;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Overlapped.Offset = 0;
+    Success = UnlockFileEx(Handle, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(!Success && ERROR_NOT_LOCKED == GetLastError());
+
+    Overlapped.Offset = BytesPerSector / 2;
+    Success = UnlockFileEx(Handle, 0, BytesPerSector, 0, &Overlapped);
+    ASSERT(Success);
+
+    Success = CloseHandle(Handle);
+    ASSERT(Success);
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        OPEN_EXISTING,
+        FILE_ATTRIBUTE_NORMAL | CreateFlags | FILE_FLAG_OVERLAPPED | FILE_FLAG_DELETE_ON_CLOSE,
+        0);
+    ASSERT(INVALID_HANDLE_VALUE != Handle);
+
+    Overlapped.Offset = 0;
+    memset(AllocBuffer[1], 0, AllocBufferSize);
+    Success = ReadFile(Handle, Buffer[1], 2 * SystemInfo.dwPageSize + BytesPerSector, &BytesTransferred, &Overlapped);
+    ASSERT(Success || ERROR_IO_PENDING == GetLastError());
+    Success = GetOverlappedResult(Handle, &Overlapped, &BytesTransferred, TRUE);
+    ASSERT(Success);
+    ASSERT(2 * SystemInfo.dwPageSize + BytesPerSector == BytesTransferred);
+    ASSERT(0 == memcmp(Buffer[0], Buffer[1], BytesTransferred));
+
+    Success = CloseHandle(Handle);
+    ASSERT(Success);
+
+    Handle = CreateFileW(FilePath,
+        GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0,
+        OPEN_EXISTING, 0, 0);
+    ASSERT(INVALID_HANDLE_VALUE == Handle);
+    ASSERT(ERROR_FILE_NOT_FOUND == GetLastError());
+
+    Success = CloseHandle(Overlapped.hEvent);
+    ASSERT(Success);
+
+    _aligned_free(AllocBuffer[0]);
+    _aligned_free(AllocBuffer[1]);
+
+    memfs_stop(memfs);
+}
+
+void lock_noncached_test(void)
+{
+    if (NtfsTests)
+    {
+        WCHAR DirBuf[MAX_PATH] = L"\\\\?\\";
+        GetCurrentDirectoryW(MAX_PATH - 4, DirBuf + 4);
+        lock_dotest(-1, L"C:", DirBuf, 0, FILE_FLAG_NO_BUFFERING);
+    }
+    if (WinFspDiskTests)
+    {
+        lock_dotest(MemfsDisk, 0, 0, 1000, FILE_FLAG_NO_BUFFERING);
+        lock_dotest(MemfsDisk, 0, 0, INFINITE, FILE_FLAG_NO_BUFFERING);
+    }
+    if (WinFspNetTests)
+    {
+        lock_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", 1000, FILE_FLAG_NO_BUFFERING);
+        lock_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", INFINITE, FILE_FLAG_NO_BUFFERING);
+    }
+}
+
+void lock_noncached_overlapped_test(void)
+{
+    if (NtfsTests)
+    {
+        WCHAR DirBuf[MAX_PATH] = L"\\\\?\\";
+        GetCurrentDirectoryW(MAX_PATH - 4, DirBuf + 4);
+        lock_overlapped_dotest(-1, L"C:", DirBuf, 0, FILE_FLAG_NO_BUFFERING);
+    }
+    if (WinFspDiskTests)
+    {
+        lock_overlapped_dotest(MemfsDisk, 0, 0, 1000, FILE_FLAG_NO_BUFFERING);
+        lock_overlapped_dotest(MemfsDisk, 0, 0, INFINITE, FILE_FLAG_NO_BUFFERING);
+    }
+    if (WinFspNetTests)
+    {
+        lock_overlapped_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", 1000, FILE_FLAG_NO_BUFFERING);
+        lock_overlapped_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", INFINITE, FILE_FLAG_NO_BUFFERING);
+    }
+}
+
+void lock_cached_test(void)
+{
+    if (NtfsTests)
+    {
+        WCHAR DirBuf[MAX_PATH] = L"\\\\?\\";
+        GetCurrentDirectoryW(MAX_PATH - 4, DirBuf + 4);
+        lock_dotest(-1, L"C:", DirBuf, 0, 0);
+    }
+    if (WinFspDiskTests)
+    {
+        lock_dotest(MemfsDisk, 0, 0, 1000, 0);
+        lock_dotest(MemfsDisk, 0, 0, INFINITE, 0);
+    }
+    if (WinFspNetTests)
+    {
+        lock_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", 1000, 0);
+        lock_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", INFINITE, 0);
+    }
+}
+
+void lock_cached_overlapped_test(void)
+{
+    if (NtfsTests)
+    {
+        WCHAR DirBuf[MAX_PATH] = L"\\\\?\\";
+        GetCurrentDirectoryW(MAX_PATH - 4, DirBuf + 4);
+        lock_overlapped_dotest(-1, L"C:", DirBuf, 0, 0);
+    }
+    if (WinFspDiskTests)
+    {
+        lock_overlapped_dotest(MemfsDisk, 0, 0, 1000, 0);
+        lock_overlapped_dotest(MemfsDisk, 0, 0, INFINITE, 0);
+    }
+    if (WinFspNetTests)
+    {
+        lock_overlapped_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", 1000, 0);
+        lock_overlapped_dotest(MemfsNet, L"\\\\memfs\\share", L"\\\\memfs\\share", INFINITE, 0);
+    }
+}
+
+void lock_tests(void)
+{
+    TEST(lock_noncached_test);
+    TEST(lock_noncached_overlapped_test);
+    TEST(lock_cached_test);
+    TEST(lock_cached_overlapped_test);
+}
diff --git a/tst/winfsp-tests/winfsp-tests.c b/tst/winfsp-tests/winfsp-tests.c
index cda0dece..cc367ee5 100644
--- a/tst/winfsp-tests/winfsp-tests.c
+++ b/tst/winfsp-tests/winfsp-tests.c
@@ -15,6 +15,7 @@ int main(int argc, char *argv[])
     TESTSUITE(security_tests);
     TESTSUITE(rdwr_tests);
     TESTSUITE(flush_tests);
+    TESTSUITE(lock_tests);
     TESTSUITE(dirctl_tests);
 
     tlib_run_tests(argc, argv);