The method '[]' was called on null Flutter - flutter

Question

I try to make some unit tests on a login funtion in flutter and I have an error that I can't fix.
This is the test:
test('Register (success)', () async {
var auth = AuthService();
var result = await auth.login("test", "123456");
var json = jsonDecode(result.toString());
expect(json['success'], true);
});
This is the function called by the test:
login(name, password) async {
if (name.toString().isEmpty || password.toString().isEmpty) {
return "Error: empty field";
}
return await dio.post('https://itsmilife.herokuapp.com/authenticate',
data: {"name": name, "password": password},
options: Options(contentType: Headers.formUrlEncodedContentType))
}
This is the function that sent the informations:
authenticate: function(req, res) {
User.findOne({
name: req.body.name
}, function (err, user) {
if (err) throw err
if (!user) {
res.status(403).send({success: false, msg: 'Authentication Failed, User not found'})
} else {
user.comparePassword(req.body.password, function (err, isMatch) {
if (isMatch && !err) {
var token = jwt.encode(user, config.secret)
res.json({success: true, token: token, user: user})
}
else {
return res.status(403).send({success: false, msg: 'Authentication failed wrong password'})
}
})
}
})
},
I have the error when I launch the test:
NoSuchMethodError: The method '[]' was called on null.
Receiver: null
Tried calling: []("success")
dart:core Object.noSuchMethod
test\widget_test.dart 24:16 main.<fn>
I don't understand how to fix the probleme.

Answer 1

Try something like this:
Future<bool> login(name, password) async {
if (name.toString().isEmpty || password.toString().isEmpty) {
return false;
}
var responseFromServer = await dio.post(
'https://itsmilife.herokuapp.com/authenticate',
data: {"name": name, "password": password},
options: Options(contentType: Headers.formUrlEncodedContentType));
if (responseFromServer == null || responseFromServer.statusCode != 200) {
return false;
}
return true;
}
Also, make your test like:
test('Register (success)', () async {
var auth = AuthService();
var result = await auth.login("test", "123456");
expect(result, true);
});