test: scan cubit unit test

test/scan/cubit/scan_cubit_test.dart

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+import 'package:bloc_test/bloc_test.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:qr_code/scan/cubit/scan_cubit.dart';
+import 'package:qr_code_repository/qr_code_repository.dart';
+
+class MockQrCodeRepository extends Mock implements QrCodeRepository {}
+
+void main() {
+  late QrCodeRepository qrCodeRepository;
+  const qrCode = 'as9dh89ahda88ss9';
+
+  setUp(() {
+    qrCodeRepository = MockQrCodeRepository();
+  });
+
+  ScanCubit buildCubit() => ScanCubit(qrCodeRepository: qrCodeRepository);
+
+  group('constructor', () {
+    test('works properly', () {
+      expect(buildCubit, returnsNormally);
+    });
+
+    test('has correct initial state', () {
+      expect(buildCubit().state, equals(const ScanState()));
+    });
+
+    blocTest<ScanCubit, ScanState>(
+      'emits successful true when repository fetches correctly',
+      build: buildCubit,
+      setUp: () {
+        when(() => qrCodeRepository.validateQrCode()).thenAnswer(
+          (_) async => true,
+        );
+      },
+      act: (cubit) => cubit.validateQrCode(qrCode: qrCode),
+      expect: () => [
+        const ScanState(
+          status: ScanStatus.success,
+          isValid: true,
+        )
+      ],
+    );
+
+    blocTest<ScanCubit, ScanState>(
+      'emits successful false when repository fetches correctly',
+      build: buildCubit,
+      setUp: () {
+        when(() => qrCodeRepository.validateQrCode()).thenAnswer(
+          (_) async => false,
+        );
+      },
+      act: (cubit) => cubit.validateQrCode(qrCode: qrCode),
+      expect: () => [
+        const ScanState(
+          status: ScanStatus.success,
+          isValid: false,
+        )
+      ],
+    );
+
+    blocTest<ScanCubit, ScanState>(
+      'emits failure false when repository throw',
+      build: buildCubit,
+      setUp: () {
+        when(() => qrCodeRepository.validateQrCode()).thenThrow(
+          Exception('Ops'),
+        );
+      },
+      act: (cubit) => cubit.validateQrCode(qrCode: qrCode),
+      expect: () => [
+        const ScanState(
+          status: ScanStatus.failure,
+        )
+      ],
+    );
+  });
+}