Why not mock the payment gateway?

[AdamEsterle]

I am new to fakes, but I think I am understanding them albeit slowly.
To me they feel a little too fake - for lack of a better word.

Instead of:
$this->assertEquals(9750, $this->paymentGateway->totalCharges());
Which then has to have code irrelevant to the rest of your app (storing the charges as an array and then summing them)

Why not use a mock on the real StripeGateway and just verify that "charge" was called with parameter 9750?

Any shedding of light on this situation (when to use a fake or a mock) would be greatly appreciated.

[adamwathan]

Hey Adam! I'm going try go make time tonight to answer this in more detail, but in the mean time here's a blog post I wrote a while back that goes into some of the benefits of fakes vs. mocks:

https://adamwathan.me/2016/01/25/writing-your-own-test-doubles/