You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: win.rs
    path of file: ./repos/windows-rs/crates/tests/reserved/tests
    
    the code of the file until where you have to start completion: use windows::{
    core::*, Win32::Foundation::*, Win32::System::Registry::*, Win32::System::Threading::*,
    Win32::UI::WindowsAndMessaging::*,
};

/// Tests a few APIs that have reserved parameters to ensure they can be called with `None`.
#[test]
fn test() -> Result<()> {
    unsafe {
        assert_eq!(InSendMessageEx(None), ISMEX_NOSEND);
        assert!(CreateThreadpool(None).0 != 0);

      
    
fn test() -> Result<()> {
    unsafe {
        assert_eq!(InSendMessageEx(None), ISMEX_NOSEND);
        assert!(CreateThreadpool(None).0 != 0);

        assert_eq!(
            TrackPopupMenu(
                HMENU(0),
                TPM_LEFTBUTTON,
                1,
                2,
                0,
                HWND(0),
                Default::default(),
            ),
            FALSE
        );

        let mut key = HKEY::default();
        RegOpenKeyExA(HKEY_CLASSES_ROOT, s!(r".txt"), 0, KEY_QUERY_VALUE, &mut key).ok()?;
        let mut len = 0;
        RegQueryValueExA(key, s!("Content Type"), None, None, None, Some(&mut len)).ok()?;
        let mut buffer = vec![0u8; (len) as usize];
        RegQueryValueExA(
            key,
            s!("Content Type"),
            None,
            None,
            Some(buffer.as_mut_ptr() as _),
            Some(&mut len),
        )
        .ok()?;
        assert_eq!(String::from_utf8_lossy(&buffer), "text/plain\0");
        Ok(())
    }
}