Tests for errors from Apple

[nathany]

I'd like some tests for errors from Apple but without actually hitting Apple's servers in the test suite.

Status code	Description
0	No errors encountered
1	Processing error
2	Missing device token
3	Missing topic
4	Missing payload
5	Invalid token size
6	Invalid topic size
7	Invalid payload size
8	Invalid token
10	Shutdown
255	None (unknown)

I'm thinking about mockConn having a special device token that results in 8 Invalid token, or that sort of thing. A bit like test credit cards.

My thought is to only do this for tests within the apns package, not impacting the callers of this library in any way.

[nathany]

Of course we also need to get a better feel for how errors from Apple occur in real life (readErrors). Using a production device token with a sandbox cert setup should do the trick.

[nathany]

Validations before sending data should be able to prevent a good number of these.

Still, there are errors that can occur at any time.

[taylortrimble]

I think I'd prefer having a connection that satisfies the interface, but is initialized with a specific status code to return. Seems more explicit.

[nathany]

True.

We should be able to use validations to avoid errors 2-8. I would like to separate out the preparation of the data to send Apple from the actual sending.