Stripe Notice Undefined Property (MetaData) in Unit Tests

Hi Folks!

I have created a unit test in order to proof if the metadata of a Stipe customer can be updated. When I filter the test everything runs successfully hoewever if I run the test suit I recieve notices: Stripe Notice: Undefined property of Stripe\StripeObject instance: billing_title. The billing_title is a metadata for a stripe user. Here is how I test it right now:

$user = factory(User::class)->create();
$user->createOrGetStripeCustomer();

        $billingData = [
            'name' => $user->name,
            'metadata' => [
                'billing_title'  => 'Dr. Prof. B',
                'billing_name'   => 'Kill Bill',
            ],
            'phone' => '111111 B',
            'address' => [
                'line1' => 'Slaughter Road 6B',
                'postal_code' => '1111 B',
                'city' => 'Tinker Bell B',
            ]
        ];

        $user->updateStripeCustomer($billingData);

        $billingDataAssertion = [
            'title' => 'Dr. Prof. B',
            'name' => 'Kill Bill',
            'company_name' => 'Slaughter Road 6B',
            'location' => '1111 B Tinker Bell B'
        ];

        $this->assertEquals($user->billing_address, $billingDataAssertion);

The test does not fail. However I have these notices:

PHPUnit 8.5.2 by Sebastian Bergmann and contributors.

................................................................. 65 / 94 ( 69%)
.........Stripe Notice: Undefined property of Stripe\StripeObject instance: billing_title
.Stripe Notice: Undefined property of Stripe\StripeObject instance: billing_title
Stripe Notice: Undefined property of Stripe\StripeObject instance: billing_title
Stripe Notice: Undefined property of Stripe\StripeObject instance: billing_title
...................                                     94 / 94 (100%)

Time: 22.32 seconds, Memory: 46.50 MB

OK (94 tests, 178 assertions)

It seems that everything is working. In production the metadata will be set and I receive the correct billing address. Do I have to worry about these notices? Can I disable them?

Best regards Alexander