AssertJ exception handling (feat.assertThat+isInstanceOf)

Question

I have been on this problem for hours but couldn't get close to solution. Any help will be appreciated.

public static int enterTheAmount(){
    int final LOTTO_PRICE = 1000;
    int amount = Integer.parseInt(Console.readLine());
    if(amount%LOTTO_PRICE!=0) throw new IllegalArgumentException();

    return amount/LOTTO_PRICE;
}

Here, a user is going to enter a number, and if the number is not divisible by 1000, it throws an exception.

void validateTheEnteredAmount(){
    final String INVALID_NUMBER = "1234";
    InputStream in = new ByteArrayInputStream(INVALID_NUMBER.getBytes());
    System.setIn(in);
    assertThat(Application.enterTheAmount()).
            isInstanceOf(IllegalArgumentException.class);
}

And I want to know when invalid number is entered, illegalArgumentException is thrown. I used assertThat method & isInstanceOf methods to validate. but for some reason, the test keeps failing.. Anyone with clues, please help

i used inputStream to store the number into the scanner. On the console, it shows that illegalargumentexception is thrown, but the test fails..

Answer 1

In the same situation I added a variable with Class type :

private Class exceptionClass;

And I will initialize it in a catch block as below:

public void updateBalance() {
        try {
            Account account = accountRepository.findById(id).get();
            account.setBalance(balance);
            accountRepository.save(account);
        } catch (Exception e) {
            exceptionClass = e.getClass();
        } 
    }

And I wrote a method for my class that will check the result like below:

boolean hasObjectOptimisticLockingFailure() {
    return this.exceptionClass == ObjectOptimisticLockingFailureException.class;
 }

Then in my test method I checked it with below assertion statement:

assertTrue(account1.hasObjectOptimisticLockingFailure() 
|| account2.hasObjectOptimisticLockingFailure());

I think you can do the same for your codes!!