// Act
        SmbFileHandleImpl opened = handle.ensureOpen();

        // Assert
        assertSame(fh, opened);
        assertTrue(handle.isOpen(), "Handle should report open after ensureOpen");
        verify(pipe, times(1)).openUnshared(eq("\\\\pipe\\\\foo"), eq(0), anyInt(), anyInt(), eq(SmbConstants.ATTR_NORMAL), eq(0));
    }

    @Test
    @DisplayName("ensureOpen throws when handle already closed")

    }

    @Test
    @DisplayName("ensureOpen delegates and returns the file handle")
    void ensureOpen_delegatesAndReturns() throws Exception {
        // Arrange
        SmbPipeOutputStream out = newStream();
        when(handle.ensureOpen()).thenReturn(fileHandle);

        // Act
        SmbFileHandleImpl result = out.ensureOpen();

        // Assert

    }

    @Test
    @DisplayName("ensureOpen delegates to handle")
    void ensureOpen_delegates() throws Exception {
        // Verify ensureOpen() delegates to SmbPipeHandleImpl
        SmbPipeInputStream stream = newStreamWithMinimalStubs(true);
        when(handle.ensureOpen()).thenReturn(fd);

        SmbFileHandleImpl result = stream.ensureOpen();
        assertSame(fd, result);

        return this.handle.ensureTreeConnected();
    }

    @Override
    protected synchronized SmbFileHandleImpl ensureOpen() throws CIFSException {
        return this.handle.ensureOpen();
    }

    /**
     * Gets the pipe handle implementation for this output stream.
     *
     * @return the handle
     */
    protected SmbPipeHandleImpl getHandle() {

    void write_lenZero_noIO() throws Exception {
        SmbRandomAccessFile raf = spy(newInstance("rw", false, true, false));
        // If ensureOpen is called, fail the test
        doThrow(new AssertionError("ensureOpen should not be called")).when(raf).ensureOpen();
        raf.write(new byte[1], 0, 0);
    }

    @Test
    @DisplayName("Null inputs: read(byte[]) and write* with nulls throw NPE")

        // Initially not open (isStale returns false when handle is null, not true)
        assertFalse(target.isOpen());
        assertFalse(target.isStale());

        // After ensureOpen, handle valid -> open
        SmbFileHandleImpl fh = target.ensureOpen();
        assertSame(fileHandle, fh);
        assertTrue(target.isOpen());
        assertFalse(target.isStale());

        // If handle becomes invalid, reflect stale

     */
    @Override
    public boolean isStale() {
        return !this.open || this.handle != null && !this.handle.isValid();
    }

    @Override
    public synchronized SmbFileHandleImpl ensureOpen() throws CIFSException {
        if (!this.open) {
            throw new SmbException("Pipe handle already closed");
        }

        if (!isOpen()) {

            } else {
                throw new IllegalArgumentException("Invalid mode");
            }

            try (SmbFileHandle h = ensureOpen()) {}
            this.readSize = th.getReceiveBufferSize() - 70;
            this.writeSize = th.getSendBufferSize() - 70;

            if (th.hasCapability(SmbConstants.CAP_LARGE_READX)) {

            pipe.send(new TransCallNamedPipe(path, b, off, len), new TransCallNamedPipeResponse(pipe));
        } else if ((pipe.pipeType & SmbNamedPipe.PIPE_TYPE_TRANSACT) == SmbNamedPipe.PIPE_TYPE_TRANSACT) {
            ensureOpen();
            final TransTransactNamedPipe req = new TransTransactNamedPipe(pipe.fid, b, off, len);
            if (dcePipe) {
                req.maxDataCount = 1024;
            }

        this.access = access | SmbConstants.FILE_WRITE_DATA;

        try (SmbTreeHandleImpl th = file.ensureTreeConnected()) {
            this.smb2 = th.isSMB2();
            try (SmbFileHandleImpl fh = ensureOpen()) {
                if (append) {
                    this.fp = fh.getInitialSize();
                }
                init(th);
                if (!append && this.smb2) {