DistributionServiceTest.php

<?php

# snip...

    /**
     * @test
     */
    public function distributeCreatesANewFile()
    {
        $this->distributionRepository->findOneBySegmentName(Argument::exact('Segment 1'))
            ->shouldBeCalled()
            ->willReturn($this->distribution);

        $this->service->distribute('Segment 1');

        $this->assertDirectoryStructure([
            'root' => [
                'var' => [
                    'distribution' => [
                        'Segment 1.csv' => '',
                    ],
                ],
            ],
        ]);
    }