DodoSSH/tests/DodoSSH.Client.App.Tests/ProbedDeviceKeyStoreTests.cs

using DodoSSH.Client.App.Platform;
using DodoSSH.Client.Session;
using NSubstitute;

namespace DodoSSH.Client.App.Tests;

/// <summary>
/// That the slow probe choosing a device key store runs once, and not on the thread that asked.
/// </summary>
/// <remarks>
/// On Windows the probe creates and deletes a TPM key, and it used to run synchronously on the UI thread at
/// startup and again after every unlock. See <see cref="ProbedDeviceKeyStore"/>.
/// </remarks>
public sealed class ProbedDeviceKeyStoreTests
{
    private static CancellationToken Token => TestContext.Current.CancellationToken;

    [Fact]
    public async Task TheChoiceIsMadeOnce_OffTheCallersThread()
    {
        var asking = Environment.CurrentManagedThreadId;
        var probes = 0;
        var probedOn = 0;

        var inner = Substitute.For<IDeviceKeyStore>();

        var store = new ProbedDeviceKeyStore(() =>
        {
            Interlocked.Increment(ref probes);
            probedOn = Environment.CurrentManagedThreadId;
            return inner;
        });

        (await store.IsAvailableAsync(Token)).ShouldBeTrue();
        (await store.IsAvailableAsync(Token)).ShouldBeTrue();
        await store.TryLoadAsync(Token);

        probes.ShouldBe(1);
        probedOn.ShouldNotBe(asking);

        // Availability is the choice, not a second probe through the store it chose.
        await inner.DidNotReceive().IsAvailableAsync(Arg.Any<CancellationToken>());
        await inner.Received(1).TryLoadAsync(Arg.Any<CancellationToken>());
    }

    [Fact]
    public async Task AMachineWithNoStore_IsUnavailable_AndForgettingIsHarmless()
    {
        var store = new ProbedDeviceKeyStore(static () => new UnavailableDeviceKeyStore());

        (await store.IsAvailableAsync(Token)).ShouldBeFalse();
        (await store.TryLoadAsync(Token)).ShouldBeNull();

        await store.ForgetAsync(Token);
    }
}