Test Error State

Test Error State (isFailed)

This skill tests isFailed() and UserException handling in Cubit methods.

What This Skill Does

Tests that:

• isFailed() returns true after operation fails
• getException() returns the thrown exception
• Error state clears when operation succeeds

Instructions

Step 1: Test Error State

import 'package:bloc_superpowers/bloc_superpowers.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mocktail/mocktail.dart';

void main() {
  late UserCubit cubit;
  late MockApi mockApi;

  setUp(() {
    Superpowers.clear();
    mockApi = MockApi();
    cubit = UserCubit(api: mockApi);
  });

  tearDown(() => cubit.close());

  test('isFailed is true after error', () async {
    when(() => mockApi.getUser()).thenThrow(Exception('Network error'));

    cubit.loadUser();
    await Future.delayed(Duration.zero);

    expect(Superpowers.isFailed(UserCubit), isTrue);
  });
}

Step 2: Test Exception Retrieval

test('getException returns the thrown exception', () async {
  when(() => mockApi.getUser()).thenThrow(
    UserException('User not found'),
  );

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  expect(Superpowers.isFailed(UserCubit), isTrue);

  final exception = Superpowers.getException(UserCubit);
  expect(exception, isA<UserException>());
  expect(exception?.message, 'User not found');
});

Step 3: Test Error Clears on Success

test('error clears when operation succeeds', () async {
  // First call fails
  when(() => mockApi.getUser()).thenThrow(Exception('Network error'));

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  expect(Superpowers.isFailed(UserCubit), isTrue);

  // Second call succeeds
  when(() => mockApi.getUser()).thenAnswer((_) async => User(name: 'John'));

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  expect(Superpowers.isFailed(UserCubit), isFalse);
  expect(Superpowers.getException(UserCubit), isNull);
});

Testing Different Error Types

UserException

test('UserException is preserved', () async {
  when(() => mockApi.getUser()).thenThrow(
    UserException('Please check your connection'),
  );

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  final exception = Superpowers.getException(UserCubit);
  expect(exception?.message, 'Please check your connection');
});

Exception Converted by catchError

test('exception is converted by catchError', () async {
  // Cubit has catchError that converts exceptions
  when(() => mockApi.getUser()).thenThrow(SocketException('No internet'));

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  final exception = Superpowers.getException(UserCubit);
  // catchError converted it to UserException
  expect(exception?.message, contains('connection'));
});

With Composite Keys

test('error state with composite key', () async {
  when(() => mockApi.deleteItem('123')).thenThrow(
    UserException('Cannot delete item'),
  );

  cubit.deleteItem('123');
  await Future.delayed(Duration.zero);

  // Error is tracked per item
  expect(Superpowers.isFailed((DeleteItem, '123')), isTrue);
  expect(Superpowers.isFailed((DeleteItem, '456')), isFalse);

  final exception = Superpowers.getException((DeleteItem, '123'));
  expect(exception?.message, 'Cannot delete item');
});

Testing Error Recovery

test('manual clearException works', () async {
  when(() => mockApi.getUser()).thenThrow(Exception('Error'));

  cubit.loadUser();
  await Future.delayed(Duration.zero);

  expect(Superpowers.isFailed(UserCubit), isTrue);

  // Manually clear the exception
  Superpowers.clearException(UserCubit);

  expect(Superpowers.isFailed(UserCubit), isFalse);
  expect(Superpowers.getException(UserCubit), isNull);
});

Testing with Retry

test('error only set after all retries exhausted', () async {
  var callCount = 0;
  when(() => mockApi.getUser()).thenAnswer((_) {
    callCount++;
    throw Exception('Retry $callCount');
  });

  cubit.loadUserWithRetry();  // mix with retry: retry(maxRetries: 2)
  await Future.delayed(const Duration(seconds: 5));  // Wait for retries

  expect(Superpowers.isFailed(UserCubit), isTrue);
  expect(callCount, 3);  // Initial + 2 retries
});

Complete Test File

import 'dart:async';
import 'package:bloc_superpowers/bloc_superpowers.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mocktail/mocktail.dart';

class MockApi extends Mock implements Api {}

void main() {
  late ProductCubit cubit;
  late MockApi mockApi;

  setUp(() {
    Superpowers.clear();
    mockApi = MockApi();
    cubit = ProductCubit(api: mockApi);
  });

  tearDown(() => cubit.close());

  group('error state', () {
    test('isFailed is true after error', () async {
      when(() => mockApi.getProducts()).thenThrow(Exception('Error'));

      cubit.loadProducts();
      await Future.delayed(Duration.zero);

      expect(Superpowers.isFailed(ProductCubit), isTrue);
      expect(Superpowers.isWaiting(ProductCubit), isFalse);
    });

    test('getException returns UserException', () async {
      when(() => mockApi.getProducts()).thenThrow(
        UserException('Products not available'),
      );

      cubit.loadProducts();
      await Future.delayed(Duration.zero);

      final exception = Superpowers.getException(ProductCubit);
      expect(exception, isA<UserException>());
      expect(exception?.message, 'Products not available');
    });

    test('error clears on successful retry', () async {
      // First fails
      when(() => mockApi.getProducts()).thenThrow(Exception('Error'));
      cubit.loadProducts();
      await Future.delayed(Duration.zero);
      expect(Superpowers.isFailed(ProductCubit), isTrue);

      // Then succeeds
      when(() => mockApi.getProducts()).thenAnswer(
        (_) async => [Product(id: '1', name: 'Widget')],
      );
      cubit.loadProducts();
      await Future.delayed(Duration.zero);

      expect(Superpowers.isFailed(ProductCubit), isFalse);
      expect(cubit.state.products.length, 1);
    });

    test('per-item error state', () async {
      when(() => mockApi.deleteProduct('1')).thenThrow(
        UserException('Cannot delete'),
      );

      cubit.deleteProduct('1');
      await Future.delayed(Duration.zero);

      expect(Superpowers.isFailed((DeleteProduct, '1')), isTrue);
      expect(Superpowers.isFailed((DeleteProduct, '2')), isFalse);

      final exception = Superpowers.getException((DeleteProduct, '1'));
      expect(exception?.message, 'Cannot delete');
    });

    test('clearException manually clears error', () async {
      when(() => mockApi.getProducts()).thenThrow(Exception('Error'));

      cubit.loadProducts();
      await Future.delayed(Duration.zero);
      expect(Superpowers.isFailed(ProductCubit), isTrue);

      Superpowers.clearException(ProductCubit);

      expect(Superpowers.isFailed(ProductCubit), isFalse);
      expect(Superpowers.getException(ProductCubit), isNull);
    });
  });
}

Key Points

1. Use Superpowers.isFailed(key) to check error state
2. Use Superpowers.getException(key) to get the exception
3. Use Superpowers.clearException(key) to manually clear
4. Error clears automatically when operation succeeds
5. Match the key exactly as used in the Cubit's mix() call
6. Reset with Superpowers.clear() in setUp

Converted and distributed by TomeVault — claim your Tome and manage your conversions.