// method of test
/** @test */
public function it_can_create_entity()
{
	   $data = [
            'reason' => 'some reason',
            'image' => [
                UploadedFile::fake()->image('report.jpg', 200, 100)->size(1000),
            ],
        ];

        $response = $this->json('POST', "route", $data, [
            'headers' => [
                'Content-Type' => 'multipart/form-data'
            ]
        ]);

        info($response->getContent());

        $response->assertCreated();
}

// method of controller
public function store(Request $request)
{
    $request->validate([
            'reason' => ['required', 'string'],
            'image' => ['nullable', 'file', 'mimes:png,jpg,webp,bmp'],
        ]);

    // остальной код ...
}