function testAdd() {
    $hash = new Hash;
    assert($OK == $hash->add("foo","bar"));
}
function testGet() {
    $hash = new Hash;
    $hash->add("foo","bar");
    assert("bar" == $hash->get("foo"));
}
function testList() {
    $hash = new Hash;
    $hash->add("foo","bar");
    assert("foo" == $hash->listKeys());
}
function testRemove() {
    $hash = new Hash;
    $hash->add("foo","bar");
    assert($OK == $hash->remove("foo"));
}