function testPathsValid()
{
$ctx = new Context();
$ctx->push('a', 'a');
$ctx->push('a', 'a');
$ctx->push('a', 'a');
$ctx->pop('a');
$ctx->push('b', 'b');
$ctx->getNode()->valid = false;
$ctx->pop('b');
$ctx->pop('a');
$ctx->push('b', 'b');
$ctx->getNode()->valid = false;
$ctx->pop('b');
$ctx->push('c', 'c');
$ctx->pop('c');
$ctx->push('d', 'd');
$ctx->pop('d');
$ctx->pop('a');
$this->assertTrue($ctx->pathsValid([['a', 'c'], ['a', 'd']]));
$this->assertFalse($ctx->pathsValid(['a', 'a', 'b'], ['a', 'c']));
$this->assertFalse($ctx->pathsValid(['a', 'a', 'a'], ['a', 'a', 'b']));
$this->assertFalse($ctx->pathsValid(['a', 'a', 'b'], ['a', 'b']));
}