public function testNegativeComponents()
{
// 1 -- 2 3 --[-1]--> 4
// ^ |
// \---[-2]----/
$graph = new Graph();
$v1 = $graph->createVertex(1);
$v2 = $graph->createVertex(2);
$v3 = $graph->createVertex(3);
$v4 = $graph->createVertex(4);
$e1 = $v1->createEdge($v2);
$e2 = $v3->createEdgeTo($v4)->setWeight(-1);
$e3 = $v4->createEdgeTo($v3)->setWeight(-2);
$alg = new DetectNegativeCycle($graph);
$this->assertTrue($alg->hasCycleNegative());
$cycle = $alg->getCycleNegative();
$this->assertCount(2, $cycle->getEdges());
$this->assertCount(3, $cycle->getVertices());
$this->assertTrue($cycle->getVertices()->hasVertexId(3));
$this->assertTrue($cycle->getVertices()->hasVertexId(4));
}