Try Catch Exceptions

You can test for exceptions within a test method by using a try/catch block and the fail method. * The method under test should throw an exception, so executing any line past the method is a failure. * The catch block does not have to do anything since the code is expected to reach this point.

import static org.junit.Assert.fail;
import org.junit.Test;

public class AccountTests2 {
  // ...
  @Test
  public void test_withdraw_throws_IllegalArgumentException_for_negative_value() {
    Account a = new Account(100.0);
    try {
      a.withdraw(-0.01);
      fail("Expected IllegalArgumentException");
    }
    catch (IllegalArgumentException e) {}
  }
  // ...
}

The advantage is that you can call the method several times in the same test method, each with its own try/catch block.

fail on Checked Exception

A test should fail if a method throws a checked exception when it should not. * Adding this kind of automated test ensures that any later change in the code does not break existing functionality.

@Test
public void test_withdrawException_removes_amount_from_balance() {
  Account a = new Account(100.0);
  try {
    a.withdrawException(50.0);
    assertEquals(50.0, a.getBalance(), 0.01);
  }
  catch (Exception e) {
    fail(e.toString());
  }
}

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