Extract FileSystem to a trait for better testability

Added some tests around filtering and searching by Tags. Added the
ability to use an in-memory Sqlite DB for more integration tests.

src/database/mod.rs

@@ -27,6 +27,24 @@ impl SqliteUserDao {
     }
 }
 
+#[cfg(test)]
+pub mod test {
+    use diesel::{Connection, SqliteConnection};
+    use diesel_migrations::{embed_migrations, EmbeddedMigrations, MigrationHarness};
+
+    const DB_MIGRATIONS: EmbeddedMigrations = embed_migrations!();
+
+    pub fn in_memory_db_connection() -> SqliteConnection {
+        let mut connection = SqliteConnection::establish(":memory:")
+            .expect("Unable to create in-memory db connection");
+        connection
+            .run_pending_migrations(DB_MIGRATIONS)
+            .expect("Failure running DB migrations");
+
+        return connection;
+    }
+}
+
 impl UserDao for SqliteUserDao {
     // TODO: Should probably use Result here
     fn create_user(&mut self, user: &str, pass: &str) -> Option<User> {