Java testing with scanner input

[glad hollow]

I have a createUser() method which i am trying to write a test for. It starts like this

        Scanner input = new Scanner(System.in);
        System.out.println("—Welcome to the Task Management System—");
        if (currentUser == null) {
            System.out.println("If you are an existing user press 1 to login, if you are a new user press 2 to register. By typing -1 when entered into any menu you can go back to main menu");
            String choice = input.nextLine();
            if (choice.equals("2")) {```

and i am trying to pass some inputs as if they are user inputs with mockito like this 
```public void testUserRegistration() throws SQLException {

        // Create a mock DatabaseService
        DatabaseService dbService = mock(DatabaseService.class);
        // Create a new Service with the mocked DatabaseService
        Service service = new Service(dbService,true);

        // Create a mock Scanner with predefined user inputs
        Scanner scanner = mock(Scanner.class);
        Person registeredUser = service.createUser(scanner);

        when(scanner.next()).thenReturn("2");
        when(scanner.nextLine()).thenReturn("testUser");
        when(scanner.nextLine()).thenReturn("testPassword");


        // Test the registration process
        // Verify that the createUser() method returns the expected output
        assertEquals("testUser", registeredUser.getName());
    }```
But still i think there is a problem cause test is not failing or anything. Can anyone help?

[subtle reef]

Detected code, here are some useful tools:

Formatted code

public Person createUser() {
  Scanner input = new Scanner(System.in);
  System.out.println("—Welcome to the Task Management System—");
  if (currentUser == null ) {
    System.out.println("If you are an existing user press 1 to login, if you are a new user press 2 to register. By typing -1 when entered into any menu you can go back to main menu");
    String choice = input.nextLine();
    if (choice.equals("2")) {

<@&987246399047479336> please have a look, thanks.

[subtle reef]

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[bronze sphinx]

u really shouldn't go about it like that

instead, the method should take as input an InputStream and then it can create the scanner on that

in ur real code u then pass System.in

and i ur test code u pass a StringReader instead

that way u can literally give the method essentially a plain string in ur tests

instead of having to mock anything

that said, it's really hard to understand what ur question is, since u said it works. so what did u expect, why did u expect it to fail etc

[glad hollow]

thank you for it

i think i fixed it like this String userInput = "2\nJohn\npassword"; InputStream in = new ByteArrayInputStream(userInput.getBytes()); System.setIn(in);

[subtle reef]

Detected code, here are some useful tools:

Formatted code

String userInput = "2\nJohn\npassword";
InputStream in = new ByteArrayInputStream(userInput.getBytes());
System.setIn(in);

[glad hollow]

i didnt know about InputStream

[bronze sphinx]

ur welcome. but u really shouldn't manipulate System. in itself. the method should take an InputStream as parameter instead. and ur getBytes() is technically a bug that can cause issues with encoding

just use a StringReader instead

[glad hollow]

How should i change it 🤔

            Reader in = new StringReader(userInput);
            InputStream inputStream = new InputStream() {
                @Override
                public int read() throws IOException, IOException {
                    return in.read();
                }
            };
            System.setIn(inputStream);``` this came up to my mind

[subtle reef]

Detected code, here are some useful tools:

Formatted code

String userInput = "2\nJohn\npassword";
Reader in = new StringReader(userInput);
InputStream inputStream = new InputStream() {
  @Override
  public int read() throws IOException, IOException {
    return in.read();
  }
};
System.setIn(inputStream);

[glad hollow]

Does this solve for cause issues with encoding and is it better this way?

[bronze sphinx]

nah use:

InputStream stream = new ByteArrayInputStream(exampleString.getBytes(StandardCharsets.UTF_8));

or let the method take a scanner instead

scanner accepts strings directly

so in real code u give it new Scanner(System.in)

and in test code new Scanner("foo")

that's probably the easiest approach

[glad hollow]

ok thanks man