diff --git a/core/src/local/mod.rs b/core/src/local/mod.rs
index 44d308f..4b68ed5 100644
--- a/core/src/local/mod.rs
+++ b/core/src/local/mod.rs
@@ -28,6 +28,18 @@ pub fn open(path: &Path) -> rusqlite::Result<Db> {
     Ok(Db(Mutex::new(conn)))
 }
 
+/// Open a migrated, in-memory store.
+///
+/// Exists so a CONSUMER can test against a real schema without taking a rusqlite
+/// dependency of its own just to build a `Db` — which is exactly what the desktop
+/// crate was doing before the core was extracted. The Android bindings will want the
+/// same thing.
+pub fn open_in_memory() -> rusqlite::Result<Db> {
+    let conn = Connection::open_in_memory()?;
+    schema::migrate(&conn)?;
+    Ok(Db(Mutex::new(conn)))
+}
+
 /// A one-line count summary of the store, for the startup log.
 pub fn summary(db: &Db) -> String {
     let conn = match db.0.lock() {
diff --git a/desktop/src-tauri/src/update.rs b/desktop/src-tauri/src/update.rs
index 86d589b..c343d4a 100644
--- a/desktop/src-tauri/src/update.rs
+++ b/desktop/src-tauri/src/update.rs
@@ -308,14 +308,20 @@ fn describe_check_error(detail: &str) -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use rusqlite::Connection;
-    use std::sync::Mutex;
-    use thoughtsync_core::local::schema;
+    use std::sync::atomic::{AtomicU32, Ordering};
 
     fn db() -> Db {
-        let conn = Connection::open_in_memory().expect("in-memory db");
-        schema::migrate(&conn).expect("migrate");
-        Db(Mutex::new(conn))
+        thoughtsync_core::local::open_in_memory().expect("in-memory db")
+    }
+
+    /// A scratch path nothing else will collide with. Process id keeps concurrent
+    /// `cargo test` runs apart, the counter keeps tests within one run apart — which
+    /// is all uuid was doing here, without the dependency (the core owns uuid now,
+    /// and pulling it into the desktop crate for two test filenames would be silly).
+    fn scratch_path(tag: &str) -> std::path::PathBuf {
+        static SEQ: AtomicU32 = AtomicU32::new(0);
+        let n = SEQ.fetch_add(1, Ordering::Relaxed);
+        std::env::temp_dir().join(format!("ts-{tag}-{}-{n}", std::process::id()))
     }
 
     /// The channel `update_check` would actually use.
@@ -336,7 +342,7 @@ mod tests {
     /// A scratch directory holding a marker file, named uniquely so tests can run in
     /// parallel. Dropped by the OS' temp cleanup; nothing here is worth a new dependency.
     fn data_dir_with_marker(contents: &str) -> std::path::PathBuf {
-        let dir = std::env::temp_dir().join(format!("ts-marker-{}", uuid::Uuid::new_v4()));
+        let dir = scratch_path("marker");
         std::fs::create_dir_all(&dir).expect("scratch dir");
         std::fs::write(dir.join(INSTALL_MARKER), contents).expect("write marker");
         dir
@@ -397,7 +403,7 @@ mod tests {
         // Built from source, or installed by anything that isn't install.sh.
         let db = db();
         set_channel(&db, Channel::Dev);
-        let empty = std::env::temp_dir().join(format!("ts-nomarker-{}", uuid::Uuid::new_v4()));
+        let empty = scratch_path("nomarker");
         std::fs::create_dir_all(&empty).expect("scratch dir");
         adopt_installer_channel(&db, &empty);
         assert_eq!(effective(&db), Channel::Dev);