Support supplying protocolClasses to NetworkConfiguration

[markst]

We wish to use Mocking libraries such as OHHTTPStubs or Mocker to build automated end 2 end testing solution in order to validate our Snowplow events are emitting.

Currently DefaultNetworkConnection provides an empty an array of protocolClasses to the URLSessionConfiguration
This overrides the swizzling performed by HTTPStubs.m

By adding protocolClasses property to NetworkConfiguration we enable supplying the network connection with custom protocols and prevent overriding swizzled properties during testing.

We can supply protocol classes such as:

Snowplow.createTracker() {
    NetworkConfiguration()
        .protocolClasses([CustomURLProtocol.self])

[matus-tomlein]

Hi @markst, thank you for the contribution, that's a useful change!

Could you please add an example test case to showcase how this could work?

[markst]

I guess something along these lines:

import XCTest
import Mocker

class SnowplowMocker: XCTestCase {
    var snowplowTracker: TrackerController?
    
    override func setUp() {
        let endpoint = "*.collector.snplow.net"
        snowplowTracker = Snowplow.createTracker(
            namespace: "DEBUG",
            endpoint: endpoint,
            method: .post
        ) {
            NetworkConfiguration(endpoint: endpoint, method: .post)
                .protocolClasses([MockingURLProtocol.self])
        }
    }
    
    func testScreenViewEvent() {
        let exp = expectation(description: "Expect mocked response requested")
        var mock = Mock(
            url: URL(string: "https://*.collector.snplow.net/com.snowplowanalytics.snowplow/tp2")!,
            statusCode: 200,
            data: [.post:"{}".data(using: .utf8)!]
        )
        mock.onRequestHandler = OnRequestHandler(httpBodyType: [[String:String]].self, callback: { request, postBodyArguments in
            if  let body = request.httpBodyStreamData(),
                let json = try? JSONSerialization.jsonObject(with: body, options: []) {
                // TODO: Validate the body contains expected params
                XCTAssertEqual
            }
            exp.fulfill()
        })
        mock.register()
        
        let event = ScreenView(name: "DemoScreenName", screenId: UUID())
            .type("TestType")
            .entities([])
        let _ = snowplowTracker?.track(event)

        wait(for: [exp], timeout: 5)
    }
}

[matus-tomlein]

Thanks @markst and sorry for the later reply. That example looks good, but I meant if you could please add it to the tracker tests in the PR so that we have this use case covered in CI and can detect any regression. The tracker tests already use the Mocker library so hopefully this should work just adding your snippet in.

[markst]

Sorry for delay @matus-tomlein. Understood and we'll sort it soon!