Make a Stub for nesting function in Yii2 - unit-testing

Question

I learn to use Unit test in Yii2 with Codeception, and try to check if a billing is a "daily" billing from a merchant's setting.
$this->biller->merchant->detail->rule_type == self::PERIODIC_MODE_DAILY
I don't know how to mock that rule_type value if I use a Stub::make() function.
What I tried so far is using the nested array like this (doesn't work) :
$billing = Stub::make(Billing::class, [
'status' => Billing::STATUS_ACTIVE,
'set_periodic_by' => Billing::SET_PERIODIC_BY_MERCHANT,
'biller' => [
'merchant' => [
'detail' => [
'rule_type' => Billing::PERIODIC_MODE_DAILY,
]
]
]
]);
And I also tried to mock each of the object model using another Stub::make()
$billing = Stub::make(Billing::class, [
'status' => Billing::STATUS_ACTIVE,
'set_periodic_by' => Billing::SET_PERIODIC_BY_MERCHANT,
'getBiller' => Stub::make(Biller::class, [
'getMerchant' => Stub::make(Merchant::class, [
'getDetail' => Stub::make(MerchantDetail::class, [
'rule_type' => Billing::PERIODIC_MODE_DAILY,
])
])
])
]);
How do I properly create a "nested" function return values using Stub? Any comment or answer is always welcome.

Answer 1

Casting the nested array to (object) will do
$billing = Stub::make(Billing::class, [
'status' => Billing::STATUS_ACTIVE,
'set_periodic_by' => Billing::SET_PERIODIC_BY_MERCHANT,
'getBiller' => (object) [
'merchant' => (object) [
'detail' => (object) [
'rule_type' => Billing::PERIODIC_MODE_DAILY,
]
]
]
]);