public function testVertexCanBeDeleted()
{
$graph = new Graph([1, 2, 3], [[1, 2], [2, 3], [1, 3]], true);
$graph->removeVertex(2);
$this->assertEquals(2, $graph->order);
$sinkArray = $graph->getSinkVertices();
$sourceArray = $graph->getSourceVertices();
$this->assertCount(1, $sourceArray);
$this->assertCount(1, $sinkArray);
$this->assertSame(reset($sourceArray), $graph->getVertex(1));
$this->assertSame(reset($sinkArray), $graph->getVertex(3));
$graph->removeVertex(3);
$this->assertEquals(1, $graph->order);
$sinkArray = $graph->getSinkVertices();
$sourceArray = $graph->getSourceVertices();
$this->assertCount(1, $sourceArray);
$this->assertCount(1, $sinkArray);
$this->assertSame(reset($sourceArray), reset($sinkArray));
}
