Inboxintel/tests/InboxIntel.IntegrationTests/SearchRankingTests.cs

using FluentAssertions;
using InboxIntel.Application.Abstractions;
using InboxIntel.Application.Search;
using InboxIntel.Domain.Entities;
using InboxIntel.Infrastructure.Persistence;
using InboxIntel.Infrastructure.Search;
using Microsoft.EntityFrameworkCore;
using Xunit;

namespace InboxIntel.IntegrationTests;

/// <summary>
/// SearchService now relevance-ranks (ts_rank_cd via RankCoverDensity) when a free-text
/// query is present, falling back to date order otherwise. The ranked path requires a
/// live PostgreSQL instance to exercise (EF's InMemory provider cannot translate
/// websearch_to_tsquery/RankCoverDensity) — this project deliberately avoids a hard
/// Postgres/Testcontainers dependency for tests (see AuthEndpointsTests.TestAppFactory),
/// so ranking correctness itself is verified manually/in staging, not here. What IS
/// covered: the date-order fallback, which is plain LINQ and must not regress.
/// </summary>
public class SearchRankingTests
{
    private sealed class FakeCurrentUser : ICurrentUser
    {
        public Guid UserId { get; set; }
        public bool IsAuthenticated => UserId != Guid.Empty;
    }

    [Fact]
    public async Task No_query_falls_back_to_date_descending_order()
    {
        var user = Guid.NewGuid();
        var opts = new DbContextOptionsBuilder<AppDbContext>()
            .UseInMemoryDatabase(nameof(No_query_falls_back_to_date_descending_order)).Options;

        using (var seed = new AppDbContext(opts, new FakeCurrentUser()))
        {
            var sender = new Sender { UserId = user, Address = "sender@example.com", DisplayName = "Sender" };
            seed.Senders.Add(sender);
            var baseline = DateTimeOffset.UtcNow;
            seed.Emails.Add(new Email { UserId = user, GmailMessageId = "oldest", SentAtUtc = baseline.AddDays(-2), Sender = sender });
            seed.Emails.Add(new Email { UserId = user, GmailMessageId = "newest", SentAtUtc = baseline, Sender = sender });
            seed.Emails.Add(new Email { UserId = user, GmailMessageId = "middle", SentAtUtc = baseline.AddDays(-1), Sender = sender });
            await seed.SaveChangesAsync();
        }

        using var ctx = new AppDbContext(opts, new FakeCurrentUser { UserId = user });
        var request = GmailQueryParser.Parse(null, page: 1, pageSize: 50);
        var result = await new SearchService(ctx).SearchAsync(user, request);

        result.Items.Select(i => i.GmailMessageId).Should().ContainInOrder("newest", "middle", "oldest");
    }
}