@Test
public void testEmpty() {
LinkedStackOfStrings s = new LinkedStackOfStrings();
assertTrue(s.isEmpty());
s.push("one");
assertFalse(s.isEmpty());
}
public void testPush2() {
LinkedStackOfStrings s = new LinkedStackOfStrings();
s.push("one");
s.push("two");
s.push("three");
assertFalse(s.isEmpty());
assertTrue(s.pop().equals("three"));
assertTrue(s.pop().equals("two"));
assertTrue(s.pop().equals("one"));
assertTrue(s.isEmpty());
}