test.php

<?php
	/**
	 * @covers ::generateText
	 */
	public function testGenerateText() {
		$a = p::mock(Vertex::class);
		p::when($a)->__toString()->thenReturn('a');

		$b = p::mock(Vertex::class);
		p::when($b)->__toString()->thenReturn('b');

		$c = p::mock(Vertex::class);
		p::when($c)->__toString()->thenReturn('c');

		$graph = p::mock(DirectedAdjacencyList::class);
		p::when($graph)->eachVertex()->thenReturn(call_user_func(function() use ($a, $b, $c) {
			yield $a => [];
			yield $b => [];
			yield $c => [];
		}));
		p::when($graph)->eachEdge()->thenReturn([[$a, $b], [$b, $c], [$c, $a]]);

		$printer = new GraphPrinter;
		$this->assertContains('node_0', $printer->generateText($graph));
	}