Flutter test can't found widget on almost exactly same cases - flutter

Question

I'm starting to learn flutter test unit, and i use firebase flutter login with bloc as the base. I changed some part of it on my code and the tests always fails. I tried to only changed the suspected code on flutter firebase login source code and the results is exactly the same as on my apps. Here the changed code:
signup_form.dart
...
class _EmailInput extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BlocBuilder<SignUpCubit, SignUpState>(
buildWhen: (previous, current) => previous.email != current.email,
builder: (context, state) {
return TextField(
key: const Key('signUpForm_emailInput_textField'),
onChanged: (email) => context.read<SignUpCubit>().emailChanged(email),
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
labelText: 'email',
helperText: '',
errorText: state.email.invalid ? 'Email is invalid' : null,
),
);
},
);
}
}
...
sign_up_form_test.dart
...
testWidgets('invalid email error text when email is invalid',
(tester) async {
final email = MockEmail();
when(() => email.invalid).thenReturn(true);
when(() => signUpCubit.state).thenReturn(SignUpState(email: email));
await tester.pumpWidget(
MaterialApp(
home: Scaffold(
body: BlocProvider.value(
value: signUpCubit,
child: const SignUpForm(),
),
),
),
);
expect(find.text('Email is invalid'), findsOneWidget);
});
...
I changed the errorType so i don't need to bloat my view file (because i want to add more state later, like email registered, email invalid, email empty, and on password i can put like minimum 8 char, need uppercase etc.). I added errorText getter on Email model (this getter is not exist on vanilla flutter firebase login)
email.dart
...
/// Get error message
///
/// Return error in #String
String? get errorText {
String? errorMessage;
if (invalid) {
errorMessage = 'Email is invalid';
}
return errorMessage;
}
...
and so I changed the errorText on Textfield to
signup_form.dart
...
decoration: InputDecoration(
labelText: 'email',
helperText: '',
errorText: state.email.errorText,
),
...
they should act exactly the same right? because state.email.invalid is accessing invalid getter so in email.dart is excatly the same as accessing invalid directly. I even changed the code to like below but the results still same
email.dart
...
String? get errorText => invalid ? 'invalid email' : null;
...
Do I use wrong test code? or I misunderstand how unit test work? I really hope I can se behind the results when testing is running because when I test it myself, I see no difference between them. Even when I only change the errorText value from signup_form.dart back to original, the test unit is success again, (so only errorText: state.email.invalid ? 'Email is invalid' : null, and errorText: state.email.errorText, is difference, where errorText is String? get errorText => invalid ? 'Email is invalid' : null;).
P.S. I don't mind if you ask me to write more code here, I just don't want my questions become too long so I skipped most of the codes related to this. btw I'm using Cubit to detect the change of the state.