What causes "Not mock connection" in SeaQL/sea-orm?

Build the connection with MockDatabase::new(DatabaseBackend::Postgres).into_connection() before calling as_mock_connection

SeaQL/sea-orm · error

Not mock connection

Error message

Not mock connection

What it means

as_mock_connection() unwraps the DatabaseConnection's inner enum to a MockDatabaseConnection. It panics when the connection was created as a real database (sqlx pool or rusqlite) or is Disconnected, because there is no mock connection to return. The library panics rather than returning Result because this is a test-support API whose misuse is a programming error.

Source

Thrown at sea-orm-sync/src/database/db_connection.rs:535

                    .map_err(TransactionError::Connection)?;
                transaction.run(_callback)
            }
            DatabaseConnectionType::Disconnected => Err(conn_err("Disconnected").into()),
        }
    }
}

#[cfg(feature = "mock")]
impl DatabaseConnection {
    /// Generate a database connection for testing the Mock database
    ///
    /// # Panics
    ///
    /// Panics if [DbConn] is not a mock connection.
    pub fn as_mock_connection(&self) -> &crate::MockDatabaseConnection {
        match &self.inner {
            DatabaseConnectionType::MockDatabaseConnection(mock_conn) => mock_conn,
            _ => panic!("Not mock connection"),
        }
    }

    /// Get the transaction log as a collection Vec<[crate::Transaction]>
    ///
    /// # Panics
    ///
    /// Panics if the mocker mutex is being held by another thread.
    pub fn into_transaction_log(self) -> Vec<crate::Transaction> {
        let mut mocker = self
            .as_mock_connection()
            .get_mocker_mutex()
            .lock()
            .expect("Fail to acquire mocker");
        mocker.drain_transaction_log()
    }
}

View on GitHub (pinned to e29bcd1b41)

Solutions

Build the connection with MockDatabase::new(DatabaseBackend::Postgres).into_connection() before calling as_mock_connection
Check the backend first with conn.get_database_backend() / whether it is a mock before unwrapping
In tests, ensure the connection under test comes from the mock fixture, not a real .connect() call

Example fix

// before
let conn = Database::connect("sqlite://test.db").unwrap();
let mock = conn.as_mock_connection(); // panics
// after
let db = MockDatabase::new(DatabaseBackend::Sqlite);
let conn: DatabaseConnection = db.into_connection();
let mock = conn.as_mock_connection(); // ok

Defensive patterns

Strategy: type-guard

Validate before calling

assert!(matches!(conn.get_database_backend(), _)); // mock connections report the backend set at MockDatabase::new; prefer checking construction
let conn = MockDatabase::new(DatabaseBackend::Sqlite).into_connection();

Type guard

fn is_mock(conn: &DatabaseConnection) -> bool { std::panic::catch_unwind(|| conn.as_mock_connection()).is_ok() } // or track construction: fn from_mock(conn: &DatabaseConnection) -> bool { /* store a flag at build time */ }

Try / catch

// Rust panics are not catchable with Result; use catch_unwind only at test boundaries:
let result = std::panic::catch_unwind(|| conn.as_mock_connection());
assert!(result.is_err(), "expected mock connection");

Prevention

Always derive test connections from MockDatabase::new(...).into_connection()
Never mix real connect() and mock accessors in the same fixture
Add a helper constructor in test code that returns (DatabaseConnection, MockDatabase) as a pair

When it happens

Trigger: Calling as_mock_connection() on a DatabaseConnection built via Database::connect (real backend), connect_stream, or one that is Disconnected; only a connection obtained through MockDatabase::new(...).into_connection() satisfies the match.

Common situations: Unit tests where the fixture set up a real SQLite/Postgres connection instead of MockDatabase; copy-pasted test code mixing real and mock connections; calling the accessor on the global/default connection by mistake.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of SeaQL/sea-orm@e29bcd1b41 (2026-09-10). Data as JSON: /api/errors/24321f576f2df518. Report an issue: GitHub.