Inboxintel/tests/InboxIntel.IntegrationTests/FeatureFlagTests.cs

using FluentAssertions;
using InboxIntel.Application.Abstractions;
using InboxIntel.Domain.Entities;
using InboxIntel.Infrastructure.Features;
using InboxIntel.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Memory;
using Xunit;

namespace InboxIntel.IntegrationTests;

/// <summary>
/// Feature-flag + AI-gate contracts (docs/discovery/multi-provider/04):
/// flags are FAIL-CLOSED, and the admin master switch (ai.enabled) beats any user opt-in.
/// </summary>
public class FeatureFlagTests
{
    private sealed class FakeCurrentUser : ICurrentUser
    {
        public Guid UserId { get; set; }
        public bool IsAuthenticated => UserId != Guid.Empty;
    }

    private static AppDbContext NewDb(string name) =>
        new(new DbContextOptionsBuilder<AppDbContext>().UseInMemoryDatabase(name).Options, new FakeCurrentUser());

    private static FeatureFlagService Flags(AppDbContext db) =>
        new(db, new MemoryCache(new MemoryCacheOptions()));

    [Fact]
    public async Task Unknown_flag_is_disabled_fail_closed()
    {
        using var db = NewDb(nameof(Unknown_flag_is_disabled_fail_closed));
        (await Flags(db).IsEnabledAsync("does.not.exist")).Should().BeFalse();
    }

    [Fact]
    public async Task Enabled_flag_reads_true_disabled_reads_false()
    {
        using var db = NewDb(nameof(Enabled_flag_reads_true_disabled_reads_false));
        db.FeatureFlags.AddRange(
            new FeatureFlag { Key = "on.flag", Enabled = true },
            new FeatureFlag { Key = "off.flag", Enabled = false });
        await db.SaveChangesAsync();
        var flags = Flags(db);
        (await flags.IsEnabledAsync("on.flag")).Should().BeTrue();
        (await flags.IsEnabledAsync("off.flag")).Should().BeFalse();
    }

    [Fact]
    public async Task Ai_gate_master_flag_off_beats_user_opt_in()
    {
        using var db = NewDb(nameof(Ai_gate_master_flag_off_beats_user_opt_in));
        var user = Guid.NewGuid();
        db.FeatureFlags.Add(new FeatureFlag { Key = AiGate.MasterFlag, Enabled = false });
        db.UserSettings.Add(new UserSetting { UserId = user, AiOptIn = true });
        await db.SaveChangesAsync();

        (await new AiGate(Flags(db), db).IsAiEnabledForUserAsync(user)).Should().BeFalse();
    }

    [Fact]
    public async Task Ai_gate_flag_on_defaults_to_opted_in_but_respects_opt_out()
    {
        using var db = NewDb(nameof(Ai_gate_flag_on_defaults_to_opted_in_but_respects_opt_out));
        var optedOut = Guid.NewGuid();
        var noRow = Guid.NewGuid();
        db.FeatureFlags.Add(new FeatureFlag { Key = AiGate.MasterFlag, Enabled = true });
        db.UserSettings.Add(new UserSetting { UserId = optedOut, AiOptIn = false });
        await db.SaveChangesAsync();
        var gate = new AiGate(Flags(db), db);

        (await gate.IsAiEnabledForUserAsync(noRow)).Should().BeTrue("no settings row = default opt-in");
        (await gate.IsAiEnabledForUserAsync(optedOut)).Should().BeFalse("explicit opt-out wins while the flag is on");
    }
}