Extract ViewModel from UINavigationPath

[akaDuality]

I would like to separate data-level of stack navigation from UI level of routing. For that I can use SwiftUI's NavigationPath and CasePaths to achieve tests like that:

 @Test
 func navigationIntegration() async throws {
     sut.navigateToPhone()
     #expect(sut.path.last.is(\.phone))

     try await viewModel(route: \.phone).pass()        
     #expect(sut.path.last.is(\.sms))

     try await viewModel(route: \.sms).pass()        
     #expect(sut.path.last.is(\.passcode))

     try await viewModel(route: \.passcode).pass()

    // Assert completion of the scenario
}

This is possible by CasePath, it's beautiful:

private func viewModel<Value>(
     route casePath: KeyPath<Case<OnboardingRoute>, Case<Value>>
) throws -> Value {
     let lastRoute = try #require(sut.path.last)
     let viewModel = lastRoute[case: casePath]
        
     return try #require(viewModel)
}

Unfortunately, UINavigationPath has no access to the last element (it is closed by @_spi) and I can't extract viewModel from it.

How I can write unit tests against NavigationStackController and associated UINavigationPath?

[akaDuality]

I can create interface for function func navigate(to route: ...) and store them in an array manually, but it looks like the library can introduce more generic approach