Get more infomation on test failure

Hello,

I would like to know why this test failed:

/** @test */
public function purchaseOrderAddedViaStoreMethod()
{
    $this->withoutExceptionHandling();
    $this->actingAs(factory(User::class)->create());
    factory(Supplier::class)->create();
    factory(Staff::class)->create();

    $response = $this->post('/po', $this->data());
    $this->assertCount(1, PurchaseOrder::all());
}

But all I get is:

1. Tests\Feature\PurchaseOrderTest::purchaseOrderAddedViaStoreMethod Failed asserting that actual size 0 matches expected size 1.

Is there a way to know more about why this failed?