public static void testPersistentQueue() {
PersistentQueue<Integer> q0 = new PersistentQueue<Integer>();
assertThat(q0.size(), 0);
int i = 0;
try {
q0.peek();
i = 1;
} catch (NoSuchElementException e) {
i = 2;
}
assertThat(i, 2);
PersistentQueue<Integer> q1 = q0.enqueue(2);
assertThat(q0.size(), 0);
assertThat(q1.size(), 1);
assertThat(q1.peek(), 2);
PersistentQueue<Integer> q2 = q1.enqueue(1);
assertThat(q2.size(), 2);
assertThat(q2.peek(), 2);
PersistentQueue<Integer> q3 = q2.dequeue();
assertThat(q3.size(), 1);
assertThat(q3.peek(), 1);
assertThat(q2.size(), 2);
assertThat(q2.peek(), 2);
assertThat(q1.size(), 1);
assertThat(q1.peek(), 2);
try {
PersistentQueue<Integer> q5 = q3.enqueue(null);
i = 3;
} catch (IllegalArgumentException e) {
i = 4;
}
assertThat(i, 4);
}
