diff --git a/tests/macos_drive_tests.rs b/tests/macos_drive_tests.rs
index e573d177..385f5959 100644
--- a/tests/macos_drive_tests.rs
+++ b/tests/macos_drive_tests.rs
@@ -114,17 +114,11 @@ fn inserted_disc_scans_filesystem_and_finds_titles() {
         DeviceTarget::Path(PathBuf::from(&drive.path)),
         KeySpec::default(),
     )
-    .unwrap_or_else(|e| {
-        panic!(
-            "failed to open {} ({}): {e}",
-            drive_name(&drive),
-            drive.path
-        )
-    });
+    .unwrap_or_else(|e| panic!("failed to open {} ({}): {e}", drive_name(drive), drive.path));
     let disc = session.scan(ScanOptions::default()).unwrap_or_else(|e| {
         panic!(
             "scan failed for {} ({}): {e}",
-            drive_name(&drive),
+            drive_name(drive),
             drive.path
         )
     });
@@ -132,7 +126,7 @@ fn inserted_disc_scans_filesystem_and_finds_titles() {
     assert!(
         !disc.titles.is_empty(),
         "disc scan completed but found no titles on {} ({})",
-        drive_name(&drive),
+        drive_name(drive),
         drive.path
     );
 }
@@ -154,3 +148,180 @@ fn inserted_disc_autodetects_and_scans_titles() {
         "autodetected drive scanned the disc but found no titles"
     );
 }
+
+/// INQUIRY populates vendor / model / firmware for every enumerated drive.
+/// Blank fields would indicate the IOKit walk dropped an INQUIRY-carrying
+/// child, which would silently break drive-fingerprint keydb lookups.
+#[test]
+#[ignore = "requires an attached optical drive"]
+fn every_enumerated_drive_reports_vendor_model_firmware() {
+    let drives = list_drives();
+    assert!(!drives.is_empty(), "no optical drive enumerated");
+    for d in &drives {
+        assert!(!d.vendor.trim().is_empty(), "empty vendor for {}", d.path);
+        assert!(!d.model.trim().is_empty(), "empty model for {}", d.path);
+        assert!(
+            !d.firmware.trim().is_empty(),
+            "empty firmware for {} ({} {})",
+            d.path,
+            d.vendor,
+            d.model
+        );
+        assert!(
+            !d.path.is_empty(),
+            "empty selector path for {} {}",
+            d.vendor,
+            d.model
+        );
+    }
+}
+
+/// Opening the same drive twice back-to-back must succeed. Catches leaked
+/// exclusive-open state in the IOKit session path — a regression would
+/// surface as "device busy" on the second open.
+#[test]
+#[ignore = "requires an attached optical drive"]
+fn drive_can_be_reopened_after_close() {
+    let drives = list_drives();
+    let target = drives.first().expect("no optical drive enumerated");
+    for i in 0..3 {
+        let drive = Drive::open(Path::new(&target.path)).unwrap_or_else(|e| {
+            panic!(
+                "iter {i}: failed to reopen {} ({}): {e}",
+                drive_name(target),
+                target.path
+            )
+        });
+        drop(drive);
+    }
+}
+
+/// UHD disc scan populates the AACS 2.0 shape we advertise on the UI:
+/// bus_encryption true, MKB version present, disc_hash populated, VID set,
+/// at least one CPS unit key. Verifies the scan pipeline end-to-end for
+/// the exact disc type most likely to regress.
+#[test]
+#[ignore = "requires an inserted UHD Blu-ray; scans AACS 2.0 disc metadata"]
+fn inserted_uhd_disc_reports_full_aacs2_state() {
+    use libfreemkv::disc::DiscFormat;
+    use libfreemkv::{DeviceTarget, DiscSession, KeySpec, ScanOptions};
+
+    let mut session = DiscSession::open(DeviceTarget::Autodetect, KeySpec::default())
+        .unwrap_or_else(|e| panic!("autodetect failed to open the inserted disc: {e}"));
+    let disc = session
+        .scan(ScanOptions::default())
+        .unwrap_or_else(|e| panic!("scan failed: {e}"));
+
+    assert!(
+        matches!(disc.format, DiscFormat::Uhd),
+        "expected UHD DiscFormat, got {:?}",
+        disc.format
+    );
+    assert!(
+        disc.capacity_bytes >= 40_000_000_000,
+        "UHD capacity should be ≥ 40 GB, got {} bytes",
+        disc.capacity_bytes
+    );
+    assert!(
+        disc.layers >= 2,
+        "UHD disc should report ≥ 2 layers, got {}",
+        disc.layers
+    );
+
+    let aacs = disc.aacs.as_ref().expect("UHD disc must have AacsState");
+    assert_eq!(aacs.version, 2, "UHD disc must be AACS 2.0");
+    assert!(aacs.bus_encryption, "UHD disc must set bus_encryption");
+    assert!(
+        aacs.mkb_version.is_some_and(|v| v > 0),
+        "UHD disc must expose MKB version, got {:?}",
+        aacs.mkb_version
+    );
+    assert!(
+        aacs.disc_hash.starts_with("0x") && aacs.disc_hash.len() == 42,
+        "disc_hash should be 0x-prefixed 40 hex chars, got {:?}",
+        aacs.disc_hash
+    );
+    assert_ne!(
+        aacs.volume_id, [0u8; 16],
+        "VID must be populated after a successful AACS 2.0 handshake"
+    );
+    assert!(
+        !aacs.unit_keys.is_empty(),
+        "at least one CPS unit key expected for a scannable UHD disc"
+    );
+}
+
+/// Scan is idempotent: rescanning the same session yields the same disc
+/// hash and MKB version. Guards against stateful drift in the scan path.
+#[test]
+#[ignore = "requires an inserted Blu-ray/DVD; rescans twice"]
+fn rescan_returns_stable_disc_identity() {
+    use libfreemkv::{DeviceTarget, DiscSession, KeySpec, ScanOptions};
+
+    let mut session = DiscSession::open(DeviceTarget::Autodetect, KeySpec::default())
+        .unwrap_or_else(|e| panic!("open failed: {e}"));
+    let first_snapshot = {
+        let first = session
+            .scan(ScanOptions::default())
+            .unwrap_or_else(|e| panic!("first scan failed: {e}"));
+        first
+            .aacs
+            .as_ref()
+            .map(|a| (a.disc_hash.clone(), a.mkb_version, a.volume_id))
+    };
+    let second_snapshot = {
+        let second = session
+            .scan(ScanOptions::default())
+            .unwrap_or_else(|e| panic!("second scan failed: {e}"));
+        second
+            .aacs
+            .as_ref()
+            .map(|a| (a.disc_hash.clone(), a.mkb_version, a.volume_id))
+    };
+
+    let (Some(a), Some(b)) = (first_snapshot, second_snapshot) else {
+        return;
+    };
+    assert_eq!(a.0, b.0, "disc_hash drifted across rescans");
+    assert_eq!(a.1, b.1, "mkb_version drifted across rescans");
+    assert_eq!(a.2, b.2, "VID drifted across rescans");
+}
+
+/// `drive_has_disc` matches what `DiscSession::open + scan` actually finds.
+/// Every drive returning `Ok(true)` must be scannable; every `Ok(false)`
+/// must fail to scan. Catches enumeration/probe divergence.
+#[test]
+#[ignore = "requires an attached optical drive; probes every enumerated drive"]
+fn drive_has_disc_matches_scan_outcome() {
+    use libfreemkv::{DeviceTarget, DiscSession, KeySpec, ScanOptions};
+
+    let drives = list_drives();
+    assert!(!drives.is_empty(), "no optical drive enumerated");
+    for d in &drives {
+        match drive_has_disc(Path::new(&d.path)) {
+            Ok(true) => {
+                let mut session = DiscSession::open(
+                    DeviceTarget::Path(PathBuf::from(&d.path)),
+                    KeySpec::default(),
+                )
+                .unwrap_or_else(|e| panic!("open failed for {}: {e}", d.path));
+                let _ = session
+                    .scan(ScanOptions::default())
+                    .unwrap_or_else(|e| panic!("scan failed on drive_has_disc=true: {e}"));
+            }
+            Ok(false) => {
+                let mut session = DiscSession::open(
+                    DeviceTarget::Path(PathBuf::from(&d.path)),
+                    KeySpec::default(),
+                )
+                .unwrap_or_else(|e| panic!("open failed for empty tray {}: {e}", d.path));
+                assert!(
+                    session.scan(ScanOptions::default()).is_err(),
+                    "scan unexpectedly succeeded on drive_has_disc=false: {}",
+                    d.path
+                );
+            }
+            Err(e) => panic!("drive_has_disc errored on {}: {e}", d.path),
+        }
+    }
+}
diff --git a/tests/macos_platform_tests.rs b/tests/macos_platform_tests.rs
new file mode 100644
index 00000000..538a5d8f
--- /dev/null
+++ b/tests/macos_platform_tests.rs
@@ -0,0 +1,85 @@
+//! macOS platform-integration tests that do NOT require an optical drive.
+//!
+//! These exercise the Mac-only code paths under `platform/fs_type/macos.rs`,
+//! `io/platform_macos.rs`, and `io/writeback_file` end-to-end against the real
+//! kernel. They run under `cargo test` without `--ignored`, so CI on macOS
+//! (and the local `cargo test` a developer would run before pushing) covers
+//! them automatically.
+
+#![cfg(target_os = "macos")]
+
+use libfreemkv::WritebackFile;
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::path::PathBuf;
+
+fn tmp_path(name: &str) -> PathBuf {
+    let mut p = std::env::temp_dir();
+    let pid = std::process::id();
+    let nanos = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map(|d| d.as_nanos())
+        .unwrap_or(0);
+    p.push(format!("freemkv-macos-test-{pid}-{nanos}-{name}"));
+    p
+}
+
+#[test]
+fn writeback_file_roundtrips_write_read() {
+    let path = tmp_path("roundtrip");
+    let payload = b"freemkv writeback roundtrip on APFS";
+
+    {
+        let mut wf = WritebackFile::create(&path).expect("create WritebackFile");
+        wf.write_all(payload).expect("write");
+        wf.sync_all().expect("sync_all");
+    }
+
+    let mut f = std::fs::File::open(&path).expect("reopen for read");
+    let mut buf = Vec::new();
+    f.read_to_end(&mut buf).expect("read");
+    let _ = std::fs::remove_file(&path);
+
+    assert_eq!(buf, payload);
+}
+
+#[test]
+fn writeback_file_seek_and_patch() {
+    let path = tmp_path("seek");
+
+    let mut wf = WritebackFile::create(&path).expect("create WritebackFile");
+    wf.write_all(b"AAAAAAAA").expect("initial write");
+    wf.seek(SeekFrom::Start(3)).expect("seek back");
+    wf.write_all(b"BB").expect("patch write");
+    wf.sync_all().expect("sync_all");
+    drop(wf);
+
+    let contents = std::fs::read(&path).expect("read back");
+    let _ = std::fs::remove_file(&path);
+    assert_eq!(&contents, b"AAABBAAA");
+}
+
+#[test]
+fn writeback_file_create_with_size_hint_preallocates() {
+    let path = tmp_path("prealloc");
+    let hint: u64 = 16 * 1024 * 1024;
+
+    let mut wf = WritebackFile::create_with_size_hint(&path, hint).expect("create_with_size_hint");
+    wf.write_all(&[0xAB; 4096]).expect("write header");
+    wf.sync_all().expect("sync_all");
+    drop(wf);
+
+    // Reported file length reflects bytes written, not the preallocation.
+    let meta = std::fs::metadata(&path).expect("stat");
+    let _ = std::fs::remove_file(&path);
+    assert_eq!(
+        meta.len(),
+        4096,
+        "reported length should equal bytes written"
+    );
+}
+
+#[test]
+fn list_drives_does_not_panic_without_hardware() {
+    // Even on a Mac with no optical drive, enumeration must return cleanly.
+    let _ = libfreemkv::list_drives();
+}