public function testSubGraph()
{
$graph = new Digraph('G');
$subgraph = $graph->subgraph('foo');
$subgraph->edge(array('A', 'B'));
$this->assertCount(1, $graph->getInstructions(), "Count of instructions");
$this->assertTrue($subgraph instanceof Subgraph, "Subgraph return");
$this->assertSame('foo', $subgraph->getId(), "Subgraph identifier");
$this->assertSame($graph, $subgraph->end(), "Subgraph end");
$this->assertEquals("subgraph foo {\n A -> B;\n};\n", $subgraph->render(), "Subgraph rendering");
}
