### Question:
Precondition { public static <T> T notNull(T value, String fieldName) { if (value == null) { throw new IllegalArgumentException("Argument " + fieldName + " cannot be null."); } return value; }  static T notNull(T value, String fieldName); static String notBlank(String value, String fieldName);  }### Answer:
@Test(expected = IllegalArgumentException.class) public void throwsOnNullArgument() { Precondition.notNull(null, null); }