Mockito when().thenAnswer() not mocking future - unit-testing

Question

I have a repository class which return Future by calling another function from another class which returns same Future. And I was trying to mock the repository class using the mockito when().thenAnswer() function like this
when(mockAccountRepository.authenticateWithEmail(
email: email,
password: password,
)).thenAnswer((_) => Future.value(SignedIn(token: token)));
the repository class has this function that returns the Future
Future<AccountEvent> authenticateWithEmail({
#required String email,
#required String password,
}) {
return _accountApiProvider.authenticateWithEmail(
email: email,
password: password,
);
}
the accountApiProvider class have the bellow function which also returns same Future
Future<AccountEvent> authenticateWithPhone(
{#required String phone, #required String password}) async {
final String data = '''{"phone":"$phone","password":"$password"}''';
try {
final Response response = await _dio.post('url', data: data);
if (response.statusCode == 200) {
print(response.data);
final String token = response.data.accessToken;
return SignedIn(token: token);
} else {
return SignInError('Internal Server Error');
}
} on DioError catch (e) {
return SignInError(e.message);
}
}
So, when I run the test it doesn't return the exact mock value provided in the thenAnswer() function.