diff --git a/src/db/mod.rs b/src/db/mod.rs
index 1f58cdf..62c2756 100644
--- a/src/db/mod.rs
+++ b/src/db/mod.rs
@@ -2047,4 +2047,110 @@ mod tests {
     assert_eq!(contents, data.to_vec());
     assert_eq!(mime, Some("text/plain".to_string()));
   }
+
+  #[test]
+  fn test_fnv1a_hasher_deterministic() {
+    // Same input should produce same hash
+    let data = b"test data";
+
+    let mut hasher1 = Fnv1aHasher::new();
+    hasher1.write(data);
+    let hash1 = hasher1.finish();
+
+    let mut hasher2 = Fnv1aHasher::new();
+    hasher2.write(data);
+    let hash2 = hasher2.finish();
+
+    assert_eq!(hash1, hash2, "FNV-1a should produce deterministic hashes");
+  }
+
+  #[test]
+  fn test_fnv1a_hasher_different_input() {
+    // Different inputs should (almost certainly) produce different hashes
+    let data1 = b"test data 1";
+    let data2 = b"test data 2";
+
+    let mut hasher1 = Fnv1aHasher::new();
+    hasher1.write(data1);
+    let hash1 = hasher1.finish();
+
+    let mut hasher2 = Fnv1aHasher::new();
+    hasher2.write(data2);
+    let hash2 = hasher2.finish();
+
+    assert_ne!(
+      hash1, hash2,
+      "Different data should produce different hashes"
+    );
+  }
+
+  #[test]
+  fn test_fnv1a_hasher_known_values() {
+    // Test against known FNV-1a hash values
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(b"");
+    assert_eq!(
+      hasher.finish(),
+      0xCBF29CE484222325,
+      "Empty string hash mismatch"
+    );
+
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(b"a");
+    assert_eq!(
+      hasher.finish(),
+      0xAF63DC4C8601EC8C,
+      "Single byte hash mismatch"
+    );
+
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(b"hello");
+    assert_eq!(hasher.finish(), 0xA430D84680AABD0B, "Hello hash mismatch");
+  }
+
+  #[test]
+  fn test_fnv1a_hash_stored_in_db() {
+    // Verify hash is stored correctly and can be retrieved
+    let db = test_db();
+    let data = b"test content for hashing";
+
+    let id = db
+      .store_entry(
+        std::io::Cursor::new(data.to_vec()),
+        100,
+        1000,
+        None,
+        None,
+        DEFAULT_MAX_ENTRY_SIZE,
+      )
+      .expect("Failed to store");
+
+    // Retrieve the stored hash
+    let stored_hash: i64 = db
+      .conn
+      .query_row(
+        "SELECT content_hash FROM clipboard WHERE id = ?1",
+        [id],
+        |row| row.get(0),
+      )
+      .expect("Failed to get hash");
+
+    // Calculate hash independently
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(data);
+    let calculated_hash = hasher.finish() as i64;
+
+    assert_eq!(
+      stored_hash, calculated_hash,
+      "Stored hash should match calculated hash"
+    );
+
+    // Verify round-trip: convert back to u64 and compare
+    let stored_hash_u64 = stored_hash as u64;
+    let calculated_hash_u64 = hasher.finish();
+    assert_eq!(
+      stored_hash_u64, calculated_hash_u64,
+      "Bit pattern should be preserved in i64/u64 conversion"
+    );
+  }
 }
diff --git a/src/db/nonblocking.rs b/src/db/nonblocking.rs
index 9640e26..bdcc596 100644
--- a/src/db/nonblocking.rs
+++ b/src/db/nonblocking.rs
@@ -5,10 +5,9 @@ use rusqlite::OptionalExtension;
 use crate::db::{ClipboardDb, SqliteClipboardDb, StashError};
 
 /// Async wrapper for database operations that runs blocking operations
-/// on a thread pool to avoid blocking the async runtime.
-///
-/// Since rusqlite::Connection is not Send, we store the database path
-/// and open a new connection for each operation.
+/// on a thread pool to avoid blocking the async runtime. Since
+/// [`rusqlite::Connection`] is not Send, we store the database path and open a
+/// new connection for each operation.
 pub struct AsyncClipboardDb {
   db_path: PathBuf,
 }
@@ -139,3 +138,186 @@ impl Clone for AsyncClipboardDb {
     }
   }
 }
+
+#[cfg(test)]
+mod tests {
+  use std::collections::HashSet;
+
+  use tempfile::tempdir;
+
+  use super::*;
+
+  fn setup_test_db() -> (AsyncClipboardDb, tempfile::TempDir) {
+    let temp_dir = tempdir().expect("Failed to create temp dir");
+    let db_path = temp_dir.path().join("test.db");
+
+    // Create initial database
+    {
+      let conn =
+        rusqlite::Connection::open(&db_path).expect("Failed to open database");
+      crate::db::SqliteClipboardDb::new(conn, db_path.clone())
+        .expect("Failed to create database");
+    }
+
+    let async_db = AsyncClipboardDb::new(db_path);
+    (async_db, temp_dir)
+  }
+
+  #[test]
+  fn test_async_store_entry() {
+    smol::block_on(async {
+      let (async_db, _temp_dir) = setup_test_db();
+      let data = b"async test data";
+
+      let id = async_db
+        .store_entry(data.to_vec(), 100, 1000, None, None, 5_000_000)
+        .await
+        .expect("Failed to store entry");
+
+      assert!(id > 0, "Should return positive id");
+
+      // Verify it was stored by checking content hash
+      let hash = async_db
+        .get_content_hash(id)
+        .await
+        .expect("Failed to get hash")
+        .expect("Hash should exist");
+
+      // Calculate expected hash
+      let mut hasher = crate::db::Fnv1aHasher::new();
+      hasher.write(data);
+      let expected_hash = hasher.finish() as i64;
+
+      assert_eq!(hash, expected_hash, "Stored hash should match");
+    });
+  }
+
+  #[test]
+  fn test_async_set_expiration_and_load() {
+    smol::block_on(async {
+      let (async_db, _temp_dir) = setup_test_db();
+      let data = b"expiring entry";
+
+      let id = async_db
+        .store_entry(data.to_vec(), 100, 1000, None, None, 5_000_000)
+        .await
+        .expect("Failed to store entry");
+
+      let expires_at = 1234567890.5;
+      async_db
+        .set_expiration(id, expires_at)
+        .await
+        .expect("Failed to set expiration");
+
+      // Load all expirations
+      let expirations = async_db
+        .load_all_expirations()
+        .await
+        .expect("Failed to load expirations");
+
+      assert_eq!(expirations.len(), 1, "Should have one expiration");
+      assert!(
+        (expirations[0].0 - expires_at).abs() < 0.001,
+        "Expiration time should match"
+      );
+      assert_eq!(expirations[0].1, id, "Expiration id should match");
+    });
+  }
+
+  #[test]
+  fn test_async_mark_expired() {
+    smol::block_on(async {
+      let (async_db, _temp_dir) = setup_test_db();
+      let data = b"entry to expire";
+
+      let id = async_db
+        .store_entry(data.to_vec(), 100, 1000, None, None, 5_000_000)
+        .await
+        .expect("Failed to store entry");
+
+      async_db
+        .mark_expired(id)
+        .await
+        .expect("Failed to mark as expired");
+
+      // Load expirations, this should be empty since entry is now marked
+      // expired
+      let expirations = async_db
+        .load_all_expirations()
+        .await
+        .expect("Failed to load expirations");
+
+      assert!(
+        expirations.is_empty(),
+        "Expired entries should not be loaded"
+      );
+    });
+  }
+
+  #[test]
+  fn test_async_get_content_hash_not_found() {
+    smol::block_on(async {
+      let (async_db, _temp_dir) = setup_test_db();
+
+      let hash = async_db
+        .get_content_hash(999999)
+        .await
+        .expect("Should not fail on non-existent entry");
+
+      assert!(hash.is_none(), "Hash should be None for non-existent entry");
+    });
+  }
+
+  #[test]
+  fn test_async_clone() {
+    let (async_db, _temp_dir) = setup_test_db();
+    let cloned = async_db.clone();
+
+    smol::block_on(async {
+      // Both should work independently
+      let data = b"clone test";
+
+      let id1 = async_db
+        .store_entry(data.to_vec(), 100, 1000, None, None, 5_000_000)
+        .await
+        .expect("Failed with original");
+
+      let id2 = cloned
+        .store_entry(data.to_vec(), 100, 1000, None, None, 5_000_000)
+        .await
+        .expect("Failed with clone");
+
+      assert_ne!(id1, id2, "Should store as separate entries");
+    });
+  }
+
+  #[test]
+  fn test_async_concurrent_operations() {
+    smol::block_on(async {
+      let (async_db, _temp_dir) = setup_test_db();
+
+      // Spawn multiple concurrent store operations
+      let futures: Vec<_> = (0..5)
+        .map(|i| {
+          let db = async_db.clone();
+          let data = format!("concurrent test {}", i).into_bytes();
+          smol::spawn(async move {
+            db.store_entry(data, 100, 1000, None, None, 5_000_000).await
+          })
+        })
+        .collect();
+
+      let results: Result<Vec<_>, _> = futures::future::join_all(futures)
+        .await
+        .into_iter()
+        .collect();
+
+      let ids = results.expect("All stores should succeed");
+      assert_eq!(ids.len(), 5, "Should have 5 entries");
+
+      // All IDs should be unique
+      let unique_ids: HashSet<_> = ids.iter().collect();
+      assert_eq!(unique_ids.len(), 5, "All IDs should be unique");
+    });
+  }
+}