diff --git a/Cargo.lock b/Cargo.lock
index 0cd6b9c..9b6c2b1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -828,6 +828,16 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "etcetera"
 version = "0.11.0"
@@ -855,6 +865,12 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "af9673d8203fcb076b19dfd17e38b3d4ae9f44959416ea532ce72415a6020365"
 
+[[package]]
+name = "fastrand"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f1f227452a390804cdb637b74a86990f2a7d7ba4b7d5693aac9b4dd6defd8d6"
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.9"
@@ -1436,6 +1452,12 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
+
 [[package]]
 name = "litemap"
 version = "0.8.2"
@@ -1516,6 +1538,7 @@ dependencies = [
  "notify",
  "sea-orm",
  "symphonia",
+ "tempfile",
  "time",
  "tokio",
  "twox-hash",
@@ -2110,6 +2133,19 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6fe4565b9518b83ef4f91bb47ce29620ca828bd32cb7e408f0062e9930ba190"
+dependencies = [
+ "bitflags 2.13.0",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
@@ -2803,6 +2839,19 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "55937e1799185b12863d447f42597ed69d9928686b8d88a1df17376a097d8369"
 
+[[package]]
+name = "tempfile"
+version = "3.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
+dependencies = [
+ "fastrand",
+ "getrandom 0.4.3",
+ "once_cell",
+ "rustix",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "thiserror"
 version = "2.0.18"
diff --git a/Cargo.toml b/Cargo.toml
index 339a24f..dd7471a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,3 +17,6 @@ twox-hash = "2.1.2"
 
 sea-orm = { version = "2.0.0-rc", features = [ "sqlx-postgres", "runtime-tokio", "macros" ] }
 tokio = { version = "1", features = ["macros", "rt-multi-thread"] }
+
+[dev-dependencies]
+tempfile = "3"
diff --git a/src/db/entities.rs b/src/db/entities.rs
index 502062e..6e2e0ad 100644
--- a/src/db/entities.rs
+++ b/src/db/entities.rs
@@ -60,3 +60,98 @@ impl From<(Model, fs::Metadata)> for Item {
         )
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::item::{FileType, Item};
+
+    #[test]
+    fn item_to_active_model_fields_match() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+        let item = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            PathBuf::from("/original/path"),
+            PathBuf::from("local/path"),
+            FileType::Directory,
+            metadata,
+            None,
+        );
+        let am = ActiveModel::from(&item);
+
+        if let sea_orm::ActiveValue::Set(v) = &am.inode {
+            assert_eq!(*v, 42i64);
+        } else {
+            panic!("inode field not set");
+        }
+
+        if let sea_orm::ActiveValue::Set(v) = &am.name {
+            assert_eq!(v, "test");
+        } else {
+            panic!("name field not set");
+        }
+
+        if let sea_orm::ActiveValue::Set(v) = &am.original_path {
+            assert_eq!(v, "/original/path");
+        } else {
+            panic!("original_path field not set");
+        }
+
+        if let sea_orm::ActiveValue::Set(v) = &am.local_path {
+            assert_eq!(v, "local/path");
+        } else {
+            panic!("local_path field not set");
+        }
+
+        if let sea_orm::ActiveValue::Set(v) = &am.hash {
+            assert_eq!(*v, item.hash as i64);
+        } else {
+            panic!("hash field not set");
+        }
+    }
+
+    #[test]
+    fn file_type_string_mapping() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+
+        let item_dir = Item::new(
+            INodeNo(1),
+            INodeNo::ROOT,
+            "dir".to_string(),
+            PathBuf::from("/original/dir"),
+            PathBuf::from("local/dir"),
+            FileType::Directory,
+            metadata.clone(),
+            None,
+        );
+        let am_dir = ActiveModel::from(&item_dir);
+
+        if let sea_orm::ActiveValue::Set(v) = &am_dir.file_type {
+            assert_eq!(v, "directory");
+        } else {
+            panic!("file_type field not set for directory");
+        }
+
+        let item_file = Item::new(
+            INodeNo(2),
+            INodeNo::ROOT,
+            "file".to_string(),
+            PathBuf::from("/original/file"),
+            PathBuf::from("local/file"),
+            FileType::File,
+            metadata,
+            None,
+        );
+        let am_file = ActiveModel::from(&item_file);
+
+        if let sea_orm::ActiveValue::Set(v) = &am_file.file_type {
+            assert_eq!(v, "file");
+        } else {
+            panic!("file_type field not set for file");
+        }
+    }
+}
diff --git a/src/item.rs b/src/item.rs
index 4a447b3..2bc6135 100644
--- a/src/item.rs
+++ b/src/item.rs
@@ -82,3 +82,70 @@ impl Item {
         return hasher.finish();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn compute_hash_deterministic() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+
+        let item1 = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            PathBuf::from("/some/path"),
+            PathBuf::from("test"),
+            FileType::File,
+            metadata,
+            None,
+        );
+
+        let metadata2 = std::fs::metadata(tmp.path()).unwrap();
+        let item2 = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            PathBuf::from("/some/path"),
+            PathBuf::from("test"),
+            FileType::File,
+            metadata2,
+            None,
+        );
+
+        assert_eq!(item1.hash, item2.hash);
+    }
+
+    #[test]
+    fn compute_hash_changes_on_path_change() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+
+        let item1 = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            PathBuf::from("/some/path"),
+            PathBuf::from("test"),
+            FileType::File,
+            metadata,
+            None,
+        );
+
+        let metadata2 = std::fs::metadata(tmp.path()).unwrap();
+        let item2 = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            PathBuf::from("/different/path"),
+            PathBuf::from("test"),
+            FileType::File,
+            metadata2,
+            None,
+        );
+
+        assert_ne!(item1.hash, item2.hash);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..f639c59
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,5 @@
+pub mod db;
+pub mod item;
+pub mod music;
+pub mod origins;
+pub mod virtual_dirs;
diff --git a/src/main.rs b/src/main.rs
index aed6239..2484f3b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,15 +1,9 @@
 use clap::Parser;
-use origins::local::watcher::FileWatcher;
+use musicfs::origins::local::watcher::FileWatcher;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::time::Duration;
 
-mod db;
-mod item;
-mod music;
-mod origins;
-mod virtual_dirs;
-
 #[derive(Parser, Debug)]
 #[command(version, about, long_about = None)]
 struct Args {
@@ -39,7 +33,7 @@ async fn main() {
 
     let db = sea_orm::Database::connect(&args.database).await.unwrap();
 
-    let fs = origins::local::LocalOrigin::new(args.source.clone(), mountpoint.clone(), db)
+    let fs = musicfs::origins::local::LocalOrigin::new(args.source.clone(), mountpoint.clone(), db)
         .await
         .unwrap();
 
diff --git a/src/music/metadata.rs b/src/music/metadata.rs
index 1329ff1..71f6f78 100644
--- a/src/music/metadata.rs
+++ b/src/music/metadata.rs
@@ -408,3 +408,124 @@ fn build_vorbis_comment(metadata: &MusicMetadata) -> Vec<u8> {
 
     out
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn read_block_header_normal() {
+        let hdr = [0x04, 0x00, 0x01, 0x00];
+        let (is_last, block_type, length) = read_block_header(&hdr);
+        assert!(!is_last);
+        assert_eq!(block_type, 4);
+        assert_eq!(length, 256);
+    }
+
+    #[test]
+    fn read_block_header_last() {
+        let hdr = [0x84, 0x00, 0x00, 0x10];
+        let (is_last, block_type, length) = read_block_header(&hdr);
+        assert!(is_last);
+        assert_eq!(block_type, 4);
+        assert_eq!(length, 16);
+    }
+
+    #[test]
+    fn virtual_size_calculation() {
+        let mut metadata = MusicMetadata::default();
+        metadata.header = vec![0u8; 100];
+        metadata.picture_data_ranges = vec![(0, 50)];
+        metadata.real_audio_start = 200;
+        let file_size = 1000u64;
+        let virtual_size = metadata.virtual_size(file_size);
+        assert_eq!(virtual_size, 954);
+    }
+
+    #[test]
+    fn build_vorbis_comment_roundtrip() {
+        let mut metadata = MusicMetadata::default();
+        metadata.artist = vec!["Artist1".to_string(), "Artist2".to_string()];
+        metadata.album = "Album".to_string();
+        metadata.track_number = 3;
+        metadata.track_title = "Title".to_string();
+        metadata.other_tags = vec!["GENRE=Rock".to_string()];
+
+        let vorbis_bytes = build_vorbis_comment(&metadata);
+        let mut parsed = MusicMetadata::default();
+        parse_vorbis_comment_block(&vorbis_bytes, &mut parsed);
+
+        assert_eq!(parsed.artist, vec!["Artist1", "Artist2"]);
+        assert_eq!(parsed.album, "Album");
+        assert_eq!(parsed.track_number, 3);
+        assert_eq!(parsed.track_title, "Title");
+        assert_eq!(parsed.other_tags, vec!["GENRE=Rock"]);
+    }
+
+    #[test]
+    fn parse_vorbis_comment_multi_artist() {
+        let mut vorbis_bytes = Vec::new();
+        let vendor = b"test";
+        vorbis_bytes.extend_from_slice(&(vendor.len() as u32).to_le_bytes());
+        vorbis_bytes.extend_from_slice(vendor);
+
+        let comments = vec!["ARTIST=Artist1", "ARTIST=Artist2"];
+        vorbis_bytes.extend_from_slice(&(comments.len() as u32).to_le_bytes());
+        for comment in &comments {
+            let bytes = comment.as_bytes();
+            vorbis_bytes.extend_from_slice(&(bytes.len() as u32).to_le_bytes());
+            vorbis_bytes.extend_from_slice(bytes);
+        }
+
+        let mut metadata = MusicMetadata::default();
+        parse_vorbis_comment_block(&vorbis_bytes, &mut metadata);
+
+        assert_eq!(metadata.artist.len(), 2);
+        assert_eq!(metadata.artist[0], "Artist1");
+        assert_eq!(metadata.artist[1], "Artist2");
+    }
+
+    #[test]
+    fn extract_non_vorbis_blocks_strips_vc_and_padding() {
+        let mut header = Vec::new();
+        header.extend_from_slice(b"fLaC");
+
+        let streaminfo_data = vec![0u8; 34];
+        header.push(0x00);
+        header.extend_from_slice(&[0x00, 0x00, 0x22]);
+        header.extend_from_slice(&streaminfo_data);
+
+        let vorbis_data = vec![0u8; 50];
+        header.push(0x04);
+        header.extend_from_slice(&[0x00, 0x00, 0x32]);
+        header.extend_from_slice(&vorbis_data);
+
+        let padding_data = vec![0u8; 100];
+        header.push(0x81);
+        header.extend_from_slice(&[0x00, 0x00, 0x64]);
+        header.extend_from_slice(&padding_data);
+
+        let blocks = extract_non_vorbis_blocks(&header);
+        assert_eq!(blocks.len(), 1);
+        assert_eq!(blocks[0].0, 0);
+        assert_eq!(blocks[0].1.len(), 34);
+    }
+
+    #[test]
+    fn find_vorbis_offsets_correct() {
+        let mut metadata = MusicMetadata::default();
+        metadata.artist = vec!["TestArtist".to_string()];
+        metadata.album = "TestAlbum".to_string();
+        metadata.track_number = 1;
+        metadata.track_title = "TestTitle".to_string();
+
+        let other_blocks = vec![(0, vec![0u8; 34])];
+        let (header, expected_offset, expected_length) = build_flac_header(other_blocks, &metadata);
+        metadata.header = header;
+
+        metadata.find_vorbis_offsets();
+
+        assert_eq!(metadata.vorbis_comment_offset, expected_offset);
+        assert_eq!(metadata.vorbis_comment_length, expected_length);
+    }
+}
diff --git a/src/origins/local/file_io.rs b/src/origins/local/file_io.rs
index e4792f2..6c8027b 100644
--- a/src/origins/local/file_io.rs
+++ b/src/origins/local/file_io.rs
@@ -75,3 +75,71 @@ pub fn assemble_flac_read(
 
     return Ok(buf);
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Write;
+
+    #[test]
+    fn read_bytes_at_full_file() {
+        let mut f = tempfile::NamedTempFile::new().unwrap();
+        f.write_all(b"hello world").unwrap();
+        f.flush().unwrap();
+        let path = f.path();
+
+        let result = read_bytes_at(path, 0, 11).unwrap();
+        assert_eq!(result, b"hello world");
+    }
+
+    #[test]
+    fn read_bytes_at_offset() {
+        let mut f = tempfile::NamedTempFile::new().unwrap();
+        f.write_all(b"abcdefghij").unwrap();
+        f.flush().unwrap();
+        let path = f.path();
+
+        let result = read_bytes_at(path, 3, 4).unwrap();
+        assert_eq!(result, b"defg");
+    }
+
+    #[test]
+    fn assemble_flac_read_header_only() {
+        let header = b"HEADERDATA";
+        let result = assemble_flac_read(Path::new(""), header, &[], &[], 0, 2, 4).unwrap();
+        assert_eq!(result, b"ADER");
+    }
+
+    #[test]
+    fn assemble_flac_read_audio_region() {
+        let mut f = tempfile::NamedTempFile::new().unwrap();
+        let content: Vec<u8> = (0..20).collect();
+        f.write_all(&content).unwrap();
+        f.flush().unwrap();
+        let path = f.path();
+
+        let header = b"HDR";
+        let result = assemble_flac_read(path, header, &[], &[], 10, 5, 4).unwrap();
+        // offset=5, header_len=3, so we read from header[3..] (0 bytes) + audio at real_off=10+(5-3)=12
+        // content[12..16] = [12, 13, 14, 15]
+        assert_eq!(result, vec![12, 13, 14, 15]);
+    }
+
+    #[test]
+    fn assemble_flac_read_header_audio_boundary() {
+        let mut f = tempfile::NamedTempFile::new().unwrap();
+        let content: Vec<u8> = (0..110).collect();
+        f.write_all(&content).unwrap();
+        f.flush().unwrap();
+        let path = f.path();
+
+        let header = b"ABCD";
+        let result = assemble_flac_read(path, header, &[], &[], 100, 2, 6).unwrap();
+        // offset=2, size=6, header_len=4
+        // First 2 bytes from header[2..4] = "CD"
+        // Remaining 4 bytes from audio at real_off=100+(2+2-4)=100
+        // content[100..104] = [100, 101, 102, 103]
+        let expected = [b'C', b'D', 100, 101, 102, 103];
+        assert_eq!(result, expected);
+    }
+}
diff --git a/src/origins/local/mod.rs b/src/origins/local/mod.rs
index 6615fbe..e62940e 100644
--- a/src/origins/local/mod.rs
+++ b/src/origins/local/mod.rs
@@ -466,3 +466,97 @@ impl Filesystem for LocalOrigin {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::item::Item;
+    use crate::music::metadata::MusicMetadata;
+    use std::os::unix::fs::MetadataExt;
+    use std::path::PathBuf;
+
+    #[test]
+    fn file_to_attr_uses_real_size_for_non_flac() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+        let item = Item::new(
+            INodeNo(42),
+            INodeNo::ROOT,
+            "test".to_string(),
+            tmp.path().to_path_buf(),
+            PathBuf::from("test"),
+            FileType::File,
+            metadata.clone(),
+            None,
+        );
+
+        let attr = LocalOrigin::file_to_attr(&item);
+        assert_eq!(attr.size, metadata.size());
+    }
+
+    #[test]
+    fn file_to_attr_uses_virtual_size_for_flac() {
+        let tmp = tempfile::tempdir().unwrap();
+        let test_file = tmp.path().join("test.flac");
+        std::fs::write(&test_file, vec![0u8; 1000]).unwrap();
+        let metadata = std::fs::metadata(&test_file).unwrap();
+        let mm = MusicMetadata {
+            real_audio_start: 500,
+            header: vec![0u8; 100],
+            picture_data_ranges: vec![(0, 50)],
+            ..MusicMetadata::default()
+        };
+        let item = Item::new(
+            INodeNo(43),
+            INodeNo::ROOT,
+            "test_flac".to_string(),
+            test_file.clone(),
+            PathBuf::from("test_flac"),
+            FileType::File,
+            metadata.clone(),
+            Some(mm.clone()),
+        );
+
+        let attr = LocalOrigin::file_to_attr(&item);
+        let expected_virtual_size = mm.virtual_size(metadata.size());
+        assert_eq!(attr.size, expected_virtual_size);
+    }
+
+    #[test]
+    fn file_to_attr_kind_directory() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+        let item = Item::new(
+            INodeNo(44),
+            INodeNo::ROOT,
+            "test_dir".to_string(),
+            tmp.path().to_path_buf(),
+            PathBuf::from("test_dir"),
+            FileType::Directory,
+            metadata,
+            None,
+        );
+
+        let attr = LocalOrigin::file_to_attr(&item);
+        assert_eq!(attr.kind, fuser::FileType::Directory);
+    }
+
+    #[test]
+    fn file_to_attr_kind_file() {
+        let tmp = tempfile::tempdir().unwrap();
+        let metadata = std::fs::metadata(tmp.path()).unwrap();
+        let item = Item::new(
+            INodeNo(45),
+            INodeNo::ROOT,
+            "test_file".to_string(),
+            tmp.path().to_path_buf(),
+            PathBuf::from("test_file"),
+            FileType::File,
+            metadata,
+            None,
+        );
+
+        let attr = LocalOrigin::file_to_attr(&item);
+        assert_eq!(attr.kind, fuser::FileType::RegularFile);
+    }
+}
diff --git a/src/virtual_dirs.rs b/src/virtual_dirs.rs
index a3a38ee..db5ce17 100644
--- a/src/virtual_dirs.rs
+++ b/src/virtual_dirs.rs
@@ -119,3 +119,148 @@ pub fn restore_virtual_paths(
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::collections::HashMap;
+
+    #[test]
+    fn virtual_inode_deterministic() {
+        let ino1 = virtual_inode("foo");
+        let ino2 = virtual_inode("foo");
+        assert_eq!(ino1, ino2);
+    }
+
+    #[test]
+    fn virtual_inode_high_bit_set() {
+        let ino = virtual_inode("test");
+        assert_eq!(ino.0 & (1u64 << 63), 1u64 << 63);
+    }
+
+    #[test]
+    fn virtual_inode_different_inputs() {
+        let ino1 = virtual_inode("foo");
+        let ino2 = virtual_inode("bar");
+        assert_ne!(ino1, ino2);
+    }
+
+    #[test]
+    fn parent_inode_single_component() {
+        let ino = parent_inode_from_path(Path::new("file.txt"));
+        assert_eq!(ino, INodeNo::ROOT);
+    }
+
+    #[test]
+    fn parent_inode_multi_component() {
+        let ino = parent_inode_from_path(Path::new("a/b/c"));
+        let expected = virtual_inode("a/b");
+        assert_eq!(ino, expected);
+    }
+
+    #[test]
+    fn parent_inode_absolute_path_filtered() {
+        let ino = parent_inode_from_path(Path::new("/file"));
+        assert_eq!(ino, INodeNo::ROOT);
+    }
+
+    #[test]
+    fn ensure_virtual_dirs_single_component() {
+        let tmp = tempfile::tempdir().unwrap();
+        let source = tmp.path();
+        let mut map = BTreeMap::new();
+
+        let ino = ensure_virtual_dirs(Path::new("file.txt"), source, &mut map);
+        assert_eq!(ino, INodeNo::ROOT);
+        assert!(map.is_empty());
+    }
+
+    #[test]
+    fn ensure_virtual_dirs_creates_hierarchy() {
+        let tmp = tempfile::tempdir().unwrap();
+        let source = tmp.path();
+        let mut map = BTreeMap::new();
+
+        let ino = ensure_virtual_dirs(Path::new("a/b/file"), source, &mut map);
+
+        let a_ino = virtual_inode("a");
+        let ab_ino = virtual_inode("a/b");
+
+        assert_eq!(ino, ab_ino);
+        assert_eq!(map.len(), 2);
+        assert!(map.contains_key(&a_ino));
+        assert!(map.contains_key(&ab_ino));
+
+        let a_item = &map[&a_ino];
+        assert_eq!(a_item.parent_inode, INodeNo::ROOT);
+
+        let ab_item = &map[&ab_ino];
+        assert_eq!(ab_item.parent_inode, a_ino);
+    }
+
+    #[test]
+    fn ensure_virtual_dirs_idempotent() {
+        let tmp = tempfile::tempdir().unwrap();
+        let source = tmp.path();
+        let mut map = BTreeMap::new();
+
+        ensure_virtual_dirs(Path::new("a/b/file"), source, &mut map);
+        let size_after_first = map.len();
+
+        ensure_virtual_dirs(Path::new("a/b/file"), source, &mut map);
+        let size_after_second = map.len();
+
+        assert_eq!(size_after_first, size_after_second);
+    }
+
+    #[test]
+    fn restore_virtual_paths_skips_root() {
+        let tmp = tempfile::tempdir().unwrap();
+        let source = tmp.path();
+        let mut snapshot = BTreeMap::new();
+
+        let real_ino = INodeNo(42);
+        let real_item = Item::new(
+            real_ino,
+            INodeNo::ROOT,
+            "real_file".to_string(),
+            source.to_path_buf(),
+            PathBuf::from("real_file"),
+            FileType::File,
+            fs::metadata(source).unwrap(),
+            None,
+        );
+        snapshot.insert(real_ino, real_item);
+
+        let mut db_items = HashMap::new();
+        db_items.insert(
+            1i64,
+            Model {
+                inode: 1,
+                hash: 0,
+                name: "root".to_string(),
+                original_path: "/tmp/test".to_string(),
+                local_path: "/tmp/test".to_string(),
+                file_type: "directory".to_string(),
+            },
+        );
+        db_items.insert(
+            42i64,
+            Model {
+                inode: 42,
+                hash: 0,
+                name: "real_file".to_string(),
+                original_path: "real_file".to_string(),
+                local_path: "real_file".to_string(),
+                file_type: "file".to_string(),
+            },
+        );
+
+        restore_virtual_paths(&mut snapshot, &db_items, source);
+
+        for item in snapshot.values() {
+            assert_ne!(item.name, "/");
+            assert_ne!(item.name, "tmp");
+        }
+    }
+}
diff --git a/tests/file_io_test.rs b/tests/file_io_test.rs
new file mode 100644
index 0000000..52edb47
--- /dev/null
+++ b/tests/file_io_test.rs
@@ -0,0 +1,75 @@
+use std::io::Write;
+
+use musicfs::origins::local::file_io::assemble_flac_read;
+
+#[test]
+fn assemble_flac_read_picture_header_region() {
+    let mut f = tempfile::NamedTempFile::new().unwrap();
+    let data: Vec<u8> = (0..100).collect();
+    f.write_all(&data).unwrap();
+    f.flush().unwrap();
+    let path = f.path();
+
+    let header = b"ABCD";
+    let pic_hdr = [0x86, 0x00, 0x00, 0x05];
+    let pic_ranges = [(10u64, 5u64)];
+    let real_audio_start = 50u64;
+
+    let result = assemble_flac_read(
+        path,
+        header,
+        &[pic_hdr],
+        &pic_ranges,
+        real_audio_start,
+        4,
+        4,
+    )
+    .unwrap();
+
+    assert_eq!(result, pic_hdr);
+}
+
+#[test]
+fn assemble_flac_read_picture_data_region() {
+    let mut f = tempfile::NamedTempFile::new().unwrap();
+    let data: Vec<u8> = (0..100).collect();
+    f.write_all(&data).unwrap();
+    f.flush().unwrap();
+    let path = f.path();
+
+    let header = b"ABCD";
+    let pic_hdr = [0x86, 0x00, 0x00, 0x05];
+    let pic_ranges = [(10u64, 5u64)];
+    let real_audio_start = 50u64;
+
+    let result = assemble_flac_read(
+        path,
+        header,
+        &[pic_hdr],
+        &pic_ranges,
+        real_audio_start,
+        8,
+        5,
+    )
+    .unwrap();
+
+    assert_eq!(result, vec![10, 11, 12, 13, 14]);
+}
+
+#[test]
+fn assemble_flac_read_full_virtual_layout() {
+    let mut f = tempfile::NamedTempFile::new().unwrap();
+    let data: Vec<u8> = (0..200).map(|i| i as u8).collect();
+    f.write_all(&data).unwrap();
+    f.flush().unwrap();
+    let path = f.path();
+
+    let header = vec![0xAA; 8];
+    let real_audio_start = 100u64;
+
+    let result = assemble_flac_read(path, &header, &[], &[], real_audio_start, 0, 18).unwrap();
+
+    let mut expected = vec![0xAA; 8];
+    expected.extend_from_slice(&(100..110).map(|i| i as u8).collect::<Vec<u8>>());
+    assert_eq!(result, expected);
+}
diff --git a/tests/snapshot_test.rs b/tests/snapshot_test.rs
new file mode 100644
index 0000000..8dcdd93
--- /dev/null
+++ b/tests/snapshot_test.rs
@@ -0,0 +1,113 @@
+use std::fs;
+use std::io::Write;
+use std::sync::{Arc, Mutex};
+
+use fuser::INodeNo;
+
+use musicfs::item::FileType;
+use musicfs::origins::local::snapshot::{build_snapshot, fill_fileset};
+
+#[test]
+fn build_snapshot_empty_dir() {
+    let source = tempfile::tempdir().unwrap();
+    let dest = tempfile::tempdir().unwrap();
+
+    let snapshot = build_snapshot(source.path(), dest.path()).unwrap();
+
+    assert_eq!(snapshot.len(), 1);
+    assert!(snapshot.contains_key(&INodeNo::ROOT));
+
+    let root = &snapshot[&INodeNo::ROOT];
+    assert_eq!(root.inode, INodeNo::ROOT);
+    assert_eq!(root.parent_inode, INodeNo::ROOT);
+    assert_eq!(root.file_type, FileType::Directory);
+}
+
+#[test]
+fn build_snapshot_flat_files() {
+    let source = tempfile::tempdir().unwrap();
+    let dest = tempfile::tempdir().unwrap();
+
+    let mut f = fs::File::create(source.path().join("a.txt")).unwrap();
+    f.write_all(b"content a").unwrap();
+
+    let mut f = fs::File::create(source.path().join("b.txt")).unwrap();
+    f.write_all(b"content b").unwrap();
+
+    let mut f = fs::File::create(source.path().join("c.txt")).unwrap();
+    f.write_all(b"content c").unwrap();
+
+    let snapshot = build_snapshot(source.path(), dest.path()).unwrap();
+
+    assert_eq!(snapshot.len(), 4);
+    assert!(snapshot.contains_key(&INodeNo::ROOT));
+
+    let file_entries: Vec<_> = snapshot
+        .values()
+        .filter(|item| item.file_type == FileType::File)
+        .collect();
+    assert_eq!(file_entries.len(), 3);
+
+    for file_entry in file_entries {
+        assert_eq!(file_entry.parent_inode, INodeNo::ROOT);
+    }
+}
+
+#[test]
+fn build_snapshot_nested_dirs() {
+    let source = tempfile::tempdir().unwrap();
+    let dest = tempfile::tempdir().unwrap();
+
+    fs::create_dir(source.path().join("subdir")).unwrap();
+    let mut f = fs::File::create(source.path().join("subdir").join("file.txt")).unwrap();
+    f.write_all(b"nested content").unwrap();
+
+    let snapshot = build_snapshot(source.path(), dest.path()).unwrap();
+
+    assert!(snapshot.contains_key(&INodeNo::ROOT));
+
+    let subdir_entry = snapshot
+        .values()
+        .find(|item| item.name == "subdir" && item.file_type == FileType::Directory)
+        .expect("subdir not found");
+
+    let file_entry = snapshot
+        .values()
+        .find(|item| item.name == "file.txt" && item.file_type == FileType::File)
+        .expect("file.txt not found");
+
+    assert_eq!(subdir_entry.parent_inode, INodeNo::ROOT);
+    assert_eq!(file_entry.parent_inode, INodeNo::ROOT);
+}
+
+#[test]
+fn fill_fileset_removes_deleted() {
+    let source = tempfile::tempdir().unwrap();
+    let dest = tempfile::tempdir().unwrap();
+
+    let mut f = fs::File::create(source.path().join("file1.txt")).unwrap();
+    f.write_all(b"content 1").unwrap();
+
+    let mut f = fs::File::create(source.path().join("file2.txt")).unwrap();
+    f.write_all(b"content 2").unwrap();
+
+    let initial_snapshot = build_snapshot(source.path(), dest.path()).unwrap();
+    let map = Arc::new(Mutex::new(initial_snapshot));
+
+    assert_eq!(map.lock().unwrap().len(), 3);
+
+    fs::remove_file(source.path().join("file1.txt")).unwrap();
+
+    fill_fileset(&map, source.path(), dest.path());
+
+    let final_map = map.lock().unwrap();
+    assert_eq!(final_map.len(), 2);
+    assert!(final_map.contains_key(&INodeNo::ROOT));
+
+    let remaining_files: Vec<_> = final_map
+        .values()
+        .filter(|item| item.file_type == FileType::File)
+        .collect();
+    assert_eq!(remaining_files.len(), 1);
+    assert_eq!(remaining_files[0].name, "file2.txt");
+}