Testing

Guide on writing unit tests for moor databases

Flutter apps using moor can always be tested with integration tests running on a real device. This guide focusses on writing unit tests for a database written in moor. Those tests can be run and debugged on your computer without additional setup, you don’t need a physical device to run them.

Setup

For tests, you need to use a VmDatabase included in moor version 3.3.0 and above. You can also test your database on older moor versions by using the moor_ffi package.

For this guide, we’re going to test a very simple database that stores user names. The only important change from a regular moor database is the constructor: We make the QueryExecutor argument explicit instead of having a no-args constructor that passes a FlutterQueryExecutor to the superclass.

import 'package:moor/moor.dart';

part 'database.g.dart';

class Users extends Table {
  IntColumn get id => integer().autoIncrement()();
  TextColumn get name => text()();
}

@UseMoor(tables: [Users])
class MyDatabase extends _$MyDatabase {
  MyDatabase(QueryExecutor e) : super(e);

  @override
  int get schemaVersion => 1;

  /// Creates a user and returns their id
  Future<int> createUser(String name) {
    return into(users).insert(UsersCompanion.insert(name: name));
  }

  /// Changes the name of a user with the [id] to the [newName].
  Future<void> updateName(int id, String newName) {
    return update(users).replace(User(id: id, name: newName));
  }

  Stream<User> watchUserWithId(int id) {
    return (select(users)..where((u) => u.id.equals(id))).watchSingle();
  }
}

Installing sqlite

We can’t distribute an sqlite installation as a pub package (at least not as something that works outside of a Flutter build), so you need to ensure that you have the sqlite3 shared library installed on your system.

On macOS, it’s installed by default.

On Linux, you can use the libsqlite3-dev package on Ubuntu and the sqlite3 package on Arch (other distros will have similar packages).

On Windows, you can download ‘Precompiled Binaries for Windows’ and extract sqlite3.dll into a folder that’s in your PATH environment variable. Then restart your device to ensure that all apps will run with this PATH change.

Writing tests

We can create an in-memory version of the database by using a VmDatabase.memory() instead of a FlutterQueryExecutor. A good place to open the database is the setUp and tearDown methods from package:test:

import 'package:moor_ffi/moor_ffi.dart';
import 'package:test/test.dart';
// the file defined above, you can test any moor database of course
import 'database.dart'; 

void main() {
  MyDatabase database;

  setUp(() {
    database = MyDatabase(VmDatabase.memory());
  });
  tearDown(() async {
    await database.close();
  });
}

With that setup in place, we can finally write some tests:

test('users can be created', () async {
  final id = await database.createUser('some user');
  final user = await database.watchUserWithId(id).first;

  expect(user.name, 'some user');
});

test('stream emits a new user when the name updates', () async {
  final id = await database.createUser('first name');

  final expectation = expectLater(
    database.watchUserWithId(id).map((user) => user.name),
    emitsInOrder(['first name', 'changed name']),
  );

  await database.updateName(id, 'changed name');
  await expectation;
});

Testing migrations

Moor can help you generate code for schema migrations. For more details, see this guide.

Last modified December 18, 2020: Update testing.md to make Windows testing docs clearer (f6f17de7)