maraphon-app/tests/Marathon.UI.Tests/Services/BacktestServiceStrategyTests.cs

using FluentAssertions;
using Marathon.Application.Abstractions;
using Marathon.Application.UseCases;
using Marathon.Domain.Backtesting;
using Marathon.UI.Services;
using Microsoft.Extensions.Logging.Abstractions;
using NSubstitute;

namespace Marathon.UI.Tests.Services;

/// <summary>
/// Covers the saved-strategy surface of <see cref="BacktestService"/> — chiefly the
/// fraction↔percent conversion (domain stores fractions, the form/VM speak percent)
/// and the form-validation guard. Run-simulation behaviour is covered elsewhere.
/// </summary>
public sealed class BacktestServiceStrategyTests
{
    private readonly ISavedStrategyRepository _strategies = Substitute.For<ISavedStrategyRepository>();
    private readonly IAnomalyRepository _anomalies = Substitute.For<IAnomalyRepository>();
    private readonly IEventRepository _events = Substitute.For<IEventRepository>();
    private readonly IResultRepository _results = Substitute.For<IResultRepository>();

    private BacktestService CreateSut()
    {
        var run = new RunBacktestUseCase(_anomalies, _events, _results, NullLogger<RunBacktestUseCase>.Instance);
        var save = new SaveStrategyUseCase(_strategies, NullLogger<SaveStrategyUseCase>.Instance);
        var delete = new DeleteStrategyUseCase(_strategies, NullLogger<DeleteStrategyUseCase>.Instance);
        return new BacktestService(run, save, delete, _strategies);
    }

    [Fact]
    public async Task ListStrategiesAsync_ConvertsStoredFractionsToPercent()
    {
        var preset = new SavedStrategy(
            Guid.NewGuid(),
            "Quarter Kelly",
            new BacktestStrategy(1000m, 0.45m, StakeRule.Kelly, 50m, PercentOfBankroll: 0.03m, KellyFraction: 0.25m),
            DateTimeOffset.UtcNow);
        _strategies.ListAsync(Arg.Any<CancellationToken>()).Returns(new[] { preset });

        var vms = await CreateSut().ListStrategiesAsync(CancellationToken.None);

        vms.Should().ContainSingle();
        vms[0].Name.Should().Be("Quarter Kelly");
        vms[0].StakeRule.Should().Be(StakeRule.Kelly);
        vms[0].PercentOfBankrollPercent.Should().Be(3m);   // 0.03 fraction → 3%
        vms[0].KellyFractionPercent.Should().Be(25m);      // 0.25 fraction → 25%
    }

    [Fact]
    public async Task SaveStrategyAsync_PersistsFormPercents_AsFractions()
    {
        _strategies.GetByNameAsync(Arg.Any<string>(), Arg.Any<CancellationToken>()).Returns((SavedStrategy?)null);
        var form = new BacktestForm
        {
            StartingBankroll = 1000m,
            MinScore = 0.5m,
            StakeRule = StakeRule.PercentOfBankroll,
            FlatStake = 50m,
            PercentOfBankrollPercent = 4m,
            KellyFractionPercent = 25m,
        };

        var vm = await CreateSut().SaveStrategyAsync("PoB", form, CancellationToken.None);

        vm.PercentOfBankrollPercent.Should().Be(4m);
        await _strategies.Received(1).AddAsync(
            Arg.Is<SavedStrategy>(s => s.Name == "PoB" && s.Strategy.PercentOfBankroll == 0.04m),
            Arg.Any<CancellationToken>());
    }

    [Fact]
    public async Task SaveStrategyAsync_Throws_And_DoesNotPersist_When_FormInvalid()
    {
        var badForm = new BacktestForm { StartingBankroll = 0m }; // fails IsValid

        var act = async () => await CreateSut().SaveStrategyAsync("X", badForm, CancellationToken.None);

        await act.Should().ThrowAsync<ArgumentException>();
        await _strategies.DidNotReceive().AddAsync(Arg.Any<SavedStrategy>(), Arg.Any<CancellationToken>());
    }

    [Fact]
    public async Task DeleteStrategyAsync_DelegatesToRepository()
    {
        var id = Guid.NewGuid();

        await CreateSut().DeleteStrategyAsync(id, CancellationToken.None);

        await _strategies.Received(1).DeleteAsync(id, Arg.Any<CancellationToken>());
    }
}