ClaudeDo/tests/ClaudeDo.Worker.Tests/Usage/UsageMonitorServiceTests.cs

using ClaudeDo.Worker.Config;
using ClaudeDo.Worker.Usage;
using ClaudeDo.Worker.Usage.Interfaces;
using Microsoft.Extensions.Logging.Abstractions;

namespace ClaudeDo.Worker.Tests.Usage;

public sealed class UsageMonitorServiceTests
{
    private sealed class FakeClient : IUsageClient
    {
        public Queue<Func<UsageSnapshot>> Results { get; } = new();
        public int CallCount { get; private set; }

        public Task<UsageSnapshot> GetUsageAsync(CancellationToken ct = default)
        {
            CallCount++;
            var next = Results.Count > 0 ? Results.Dequeue() : () => throw new InvalidOperationException("no result queued");
            return Task.FromResult(next());
        }
    }

    private static UsageSnapshot MakeSnapshot() => new(new UsageBucket(1, null), null, [], DateTime.UtcNow);

    [Fact]
    public async Task TickAsync_Success_UpdatesState()
    {
        var client = new FakeClient();
        client.Results.Enqueue(MakeSnapshot);
        var state = new UsageState();
        var service = new UsageMonitorService(client, state, new WorkerConfig(), NullLogger<UsageMonitorService>.Instance);

        await service.TickAsync(CancellationToken.None);

        Assert.NotNull(state.Snapshot);
        Assert.Null(state.LastError);
    }

    [Fact]
    public async Task TickAsync_Failure_SetsErrorButDoesNotThrow()
    {
        var client = new FakeClient();
        client.Results.Enqueue(() => throw new InvalidOperationException("network unreachable"));
        var state = new UsageState();
        var service = new UsageMonitorService(client, state, new WorkerConfig(), NullLogger<UsageMonitorService>.Instance);

        await service.TickAsync(CancellationToken.None);

        Assert.Equal("network unreachable", state.LastError);
        Assert.Null(state.Snapshot);
    }

    [Fact]
    public async Task TickAsync_FailureAfterSuccess_KeepsOldSnapshot()
    {
        var client = new FakeClient();
        client.Results.Enqueue(MakeSnapshot);
        client.Results.Enqueue(() => throw new InvalidOperationException("down"));
        var state = new UsageState();
        var service = new UsageMonitorService(client, state, new WorkerConfig(), NullLogger<UsageMonitorService>.Instance);

        await service.TickAsync(CancellationToken.None);
        await service.TickAsync(CancellationToken.None);

        Assert.NotNull(state.Snapshot);
        Assert.Equal("down", state.LastError);
    }
}