@Test public void push() throws Exception {

    IntStack stack = new IntStack(4);
    stack.push(1);
    assertThat(stack.peek(), is(1));
    assertThat(stack.size(), is(1));
    stack.push(2);
    assertThat(stack.peek(), is(2));
    assertThat(stack.size(), is(2));
    stack.push(4);
    assertThat(stack.peek(), is(4));
    assertThat(stack.size(), is(3));
}