Dartz, flutter test - Can't get a Right part of Future<Either<L, R>>, instead of that - instance of Future<Either<L, R>> as a actual result

Question

This is my first try to write a test. I use the Dartz package and I don't know how to get just one part as a result of my test. The error is:

Expected: Right<dynamic, NumberTrivia>:<Right(NumberTrivia(test, 1))> Actual: <Instance of 'Future<Either<Failure, NumberTrivia>>'>

The function in repository:

abstract class NumberTriviaRepository {
  Future<Either<Failure, NumberTrivia>> getConcreteNumberTrivia(int number);
  Future<Either<Failure, NumberTrivia>> getRandomNumberTrivia();
}

The function in usecase:

class GetConcreteNumberTrivia {
  final NumberTriviaRepository numberTriviaRepository;
  GetConcreteNumberTrivia(this.numberTriviaRepository);

  Future<Either<Failure, NumberTrivia>> execute({
    required int number,
  }) async {
    return await numberTriviaRepository.getConcreteNumberTrivia(number);
  }
}

And the test class:

import 'package:dartz/dartz.dart';
import 'package:mockito/annotations.dart';
import 'package:mockito/mockito.dart';
import 'package:number_trivia/features/number_trivia/domain/entities/number_trivia.dart';
import 'package:number_trivia/features/number_trivia/domain/repositories/number_trivia_repository.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:number_trivia/features/number_trivia/domain/usecases/get_concrete_number_trivia.dart';

import 'get_concrete_number_trivia_test.mocks.dart';

@GenerateMocks([NumberTriviaRepository])
void main() {
  late GetConcreteNumberTrivia usecase;
  late MockNumberTriviaRepository mockNumberTriviaRepository;
  setUp(() {
    mockNumberTriviaRepository = MockNumberTriviaRepository();
    usecase = GetConcreteNumberTrivia(mockNumberTriviaRepository);
  });

  final tNumber = 1;
  final tNumberTrivia = NumberTrivia(text: 'test', number: tNumber);
  test('should get trivia for the number from the repository', () async {
    // arrange
    when(mockNumberTriviaRepository.getConcreteNumberTrivia(tNumber))
        .thenAnswer((_) async => Right(tNumberTrivia));
    // act
    final result = usecase.execute(number: tNumber);
    // assets
    expect(result, Right(tNumberTrivia));
    verify(mockNumberTriviaRepository.getConcreteNumberTrivia(tNumber));
    verifyNoMoreInteractions(mockNumberTriviaRepository);
  });
}

Answer 1

The issue coming because usecase.execute(number: tNumber); retuning future, use await before it.

// act
final result = await usecase.execute(number: tNumber);