public function test_keyval_representation_1()
{
$cs = array('a:x^2', 'b:1/(1+x^2)', 'c:e^(i*pi)');
foreach ($cs as $s) {
$s1[] = new stack_cas_casstring($s);
}
$at1 = new stack_cas_session($s1, null, 0);
$this->assertEquals('a:x^2; b:1/(1+x^2); c:e^(i*pi);', $at1->get_keyval_representation());
$this->assertEquals(array('a', 'b', 'c'), $at1->get_all_keys());
$at1->prune_session(1);
$this->assertEquals(array('a'), $at1->get_all_keys());
}