Expected: <false> Actual: <Closure: () => Future<bool>> in flutter unit testing - flutter

Question

I'm writing unit tests to test the authorise function below which is in AuthService class.
Future<bool> authorize() async {
AuthorizationTokenResponse? authResult;
try {
authResult = await appAuth.authorizeAndExchangeCode(
AuthorizationTokenRequest(
bsEnv.AD_CLIENT_ID!,
));
if (authResult != null) {
return true;
}
} on PlatformException catch (e) {
forgetPassword();
}
}
return false;
}
I am using Mocktail to make the mocks. Below is one written test for the authorise function mentioned in the above code.
class MockBEnv extends Mock implements BEnv {}
class MockSharedPrefsService extends Mock implements SharedPrefsService {}
class MockFlutterAppAuth extends Mock implements FlutterAppAuth {}
class MockAuthorizationServiceConfiguration extends Mock
implements AuthorizationServiceConfiguration {}
class MockAuthorizationTokenResponse extends Mock
implements AuthorizationTokenResponse {}
class MockAuthorizationTokenRequest extends Mock
implements AuthorizationTokenRequest {}
class MockTokenResponse extends Mock implements TokenResponse{}
class MockTokenRequest extends Mock implements TokenRequest{
}
void main() {
late AuthService authService;
late MockFlutterAppAuth mockFlutterAppAuth;
late MockBEnv mockBEnv;
late MockSharedPrefsService mockStorageService;
late MockAuthorizationTokenResponse mockAuthorizationTokenResponse;
late MockAuthorizationTokenRequest mockAuthorizationTokenRequest;
const tUrl = 'https://endpoint/';
const tUserImp = 'user';
const tAppLan = 'sv-SE';
const tClientId = 'client';
const tIosUri = 'ios';
const tTokenEndPoint = 'abcdeff';
setUp(() {
mockFlutterAppAuth = MockFlutterAppAuth();
mockBEnv = MockBEnv();
mockStorageService = MockSharedPrefsService();
mockAuthorizationTokenRequest = MockAuthorizationTokenRequest();
mockAuthorizationTokenResponse = MockAuthorizationTokenResponse();
authService = AuthService(
appAuth: mockFlutterAppAuth,
bsEnv: mockBEnv,
sharedPrefs: mockStorageService);
});
group('authorize', () {
test(
'should return true when the call to authorized method if result is not null',
() async {
// Arrange
when(() => mockBEnv.AD_CLIENT_ID).thenAnswer((_) => tClientId);
when(() => mockFlutterAppAuth
.authorizeAndExchangeCode(mockAuthorizationTokenRequest))
.thenAnswer((_)=> Future.value(mockAuthorizationTokenResponse));
// Act
final result = authService.authorize;
// Assert
expect(() => result(), equals(false));
});
});
}
My test fails and below is the error message I get,
Expected: < false >
Actual: <Closure: () => Future>
How can I fix this issue?

Answer 1

authService.authorize is an asynchronous method, returning a Future<bool>.
So your testcase should be
final result = await authService.authorize();
expect(result, equals(false));
The await keyword leads to an async execution that resolves the Future into an actual value