Add supervision timeout to CBMPeriphalSpec, make rssi deviation public and mutable

[nathandud]

Two changes to make the library more friendly for unit testing to address #116.

1. RSSI deviation is now an internal private(set) mutable variable that can be set via a new public function simulateRSSIDeviation. It is serves as configuration to CBCentralManagerMock. A new internal enum Deviation has been added to CBMPromixity to limit the possible values to either .default which is the current implementation of +/- 15 dBm and .none which is 0.

CBMCentralManagerMock.simulateRSSIDeviation(.none)

2. The supervisionTimeout has been added to CBMPeripheralSpec so that it can be optionally initialized with .connectable similar to the mtu and connectionInterval. Default value is 4.0 seconds to match the existing private implementation.

.connectable(
    name: "Test_Device",
    services: [],
    delegate: self,
    connectionInterval: 0.01,
    supervisionTimeout: 0,
    mtu: 32
)

These are non-breaking changes that only add functionality to the existing API. Existing clients are unaffected.

Adding the above changes to the unit test in #116 allow the tests to pass without any delays

Single test

Test Case '-[BluetoothMockExampleTests.BluetoothDelegateTests testPeripheralConnectThenOutOfRange]' passed (0.048 seconds).
Test Suite 'BluetoothDelegateTests' passed at 2025-03-10 12:52:04.728.
	 Executed 1 test, with 0 failures (0 unexpected) in 0.048 (0.049) seconds

100,000 Repeated Tests

Test Suite 'BluetoothDelegateTests' passed at 2025-03-10 13:35:49.387.
	 Executed 100000 tests, with 0 failures (0 unexpected) in 1147.365 (1164.023) seconds

[nathandud]

Had to update the implementation of the RSSI for Swift 6 clients. A public shared mutable variable rssiDeviation throws an error in Swift 6. In theory, simulateRSSIDeviation(:) is not 100% thread safe but repeated tests succeed as the internal rssiDeviation is not an oft-accessed bit of state. The entire package could be updated for Swift Concurrency but that would be a much more ambitious change.

Test Suite 'BluetoothDelegateTests' passed at 2025-03-10 19:33:55.930.
	 Executed 1000 tests, with 0 failures (0 unexpected) in 11.465 (11.629) seconds

[philips77]

Excellent work! Thank you!
I added just few minor change requests. When you fix them, I'll push a release.

[philips77]

Perhaps, instead of extending Int, there could be a computed property reporting the deviation?
You could also add a custom(_ deviation: Int) to improve it even more.

[nathandud]

I like this - it opts for a more internal implementation and maintains a clean public API.

I added a case for a custom value like you recommended. There is potential for a user to set a deviation of 10000+ and the RSSI can be something well out-of-range for its associated proximity, but it doesn't affect anything downstream and won't cause the library to crash or anything. I successfully ran multiple tests with a variety of RSSI deviation values. However, the value must be >= 0 so the absolute value is used if the user provides a negative value. I toyed with the idea of using UInt8 but that just felt clunky especially since CBProximity.Deviation is part of the public-facing API.