### Question:
SimpleUserPassBuilder extends UserPassBuilder { @Override public UserPassBuilder setUsername(final String username) { if (username == null) { throw new NullPointerException("Username cannot be null."); } this.username = username; markAsSet(Attribute.USERNAME); return this; }  @Override UserPassBuilder setPassword(final String password); @Override UserPassProduct build(); @Override UserPassBuilder setServerAddress(final URI serverAddress); @Override UserPassBuilder setUsername(final String username);  }### Answer:
@Test(expected = NullPointerException.class) public void testSetNullUsername() { builder.setUsername(null); }