}
@Test
public void push_and_pop()
{
Environment e = new EnvironmentImpl();
Runnable r1 = mockRunnable();
Runnable r2 = mockRunnable();
replay();
assertNull(e.push(Runnable.class, r1));
assertSame(r1, e.peek(Runnable.class));
assertSame(r1, e.push(Runnable.class, r2));
assertSame(r2, e.peek(Runnable.class));
assertSame(r2, e.pop(Runnable.class));
assertSame(r1, e.pop(Runnable.class));
verify();
}