ClaudeMailbox/tests/ClaudeMailbox.Tests/RaceTests.cs

using System.Net.Http.Json;
using System.Text.Json;

namespace ClaudeMailbox.Tests;

public sealed class RaceTests
{
    [Fact]
    public async Task Parallel_CheckInbox_Delivers_Each_Message_Exactly_Once()
    {
        await using var host = await TestHost.StartAsync();
        using var sender = host.NewClientFor("sender");
        using var recipient = host.NewClientFor("recipient");

        const int messageCount = 50;
        for (var i = 0; i < messageCount; i++)
        {
            var res = await sender.PostAsJsonAsync("/v1/send", new { to = "recipient", body = $"msg-{i}" });
            res.EnsureSuccessStatusCode();
        }

        // Fire multiple concurrent checks. Each message must appear in exactly one result set.
        var tasks = Enumerable.Range(0, 8).Select(async _ =>
        {
            var res = await recipient.PostAsync("/v1/check-inbox?name=recipient", null);
            res.EnsureSuccessStatusCode();
            return await res.Content.ReadFromJsonAsync<JsonElement>();
        });

        var results = await Task.WhenAll(tasks);

        var ids = new List<long>();
        foreach (var arr in results)
            foreach (var m in arr.EnumerateArray())
                ids.Add(m.GetProperty("id").GetInt64());

        Assert.Equal(messageCount, ids.Count);
        Assert.Equal(messageCount, ids.Distinct().Count());
    }
}