are you sure you told it to expect the exception?
for newer junit (>= 4.7), you can use something like (from here)
@Rule
public ExpectedException exception = ExpectedException.none();
@Test
public void testRodneCisloRok(){
exception.expect(IllegalArgumentException.class);
exception.expectMessage("error1");
new RodneCislo("891415",dopocitej("891415"));
}
and for older junit, this:
@Test(expected = ArithmeticException.class)
public void divisionWithException() {
int i = 1/0;
}