Unit Testing

FakeInjector is a tiny, in-memory injector for pure unit tests. It feeds fakes to the class under test without touching the global container — no Modular.configure, no reset, no leaks between tests.

FakeInjector

Build an injector by chaining add, then resolve with get:

import 'package:flutter_test/flutter_test.dart';
import 'package:go_router_modular/testing.dart';
 
void main() {
  test('OrderService charges through the gateway', () {
    final injector = FakeInjector.empty()
        .add<PaymentGateway>(FakePaymentGateway())
        .add<UserRepository>(FakeUserRepository());
 
    final service = OrderService(
      injector.get<PaymentGateway>(),
      injector.get<UserRepository>(),
    );
 
    expect(service.checkout(), isTrue);
  });
}

• FakeInjector.empty() — creates an empty injector.
• add<T>(T instance) — immutable: returns a new injector with T registered. The original is unchanged, so the methods chain.
• get<T>({String? key}) — resolves T.

Missing dependencies fail loudly

If you get<T>() a type you never registered, FakeInjector throws FakeInjectorMissingBindError with a message telling you exactly which type is missing and how to add it — no silent null:

FakeInjector.empty().get<PaymentGateway>();
// throws FakeInjectorMissingBindError:
// "nenhum bind registrado para o tipo PaymentGateway."

It is an InjectorReader

FakeInjector implements InjectorReader, so you can pass it anywhere one is expected — for example, to a module’s initState:

final module = CartModule();
module.initState(FakeInjector.empty().add<CartRepository>(FakeCartRepository()));

FakeInjector vs ModularTestScope

Next steps

• Overview
• Testing Events
• Dependency Injection