verify(tree).send((Request<CommonServerMessageBlockResponse>) isNull());
    }

    @Test
    @DisplayName("send with explicit null varargs propagates exception from implementation")
    void send_nullVarargsArray_throws() throws Exception {
        // Arrange: passing explicit null vararg array is edge scenario
        when(tree.send(eq(request), isNull())).thenThrow(new CIFSException("null params"));

        // Act + Assert