llm-pii-poc/tests/PiiRedaction.Core.Tests/Integration/LlmBoundaryTests.cs

using FluentAssertions;
using PiiRedaction.Core.Abstractions;
using PiiRedaction.Core.Models;
using PiiRedaction.Core.Tests.TestSupport;
using PiiRedaction.Infrastructure.Llm;

namespace PiiRedaction.Core.Tests.Integration;

[TestFixture]
public sealed class LlmBoundaryTests
{
    [Test]
    public async Task SendPromptAsync_DoesNotTransmitOriginalPii()
    {
        var capturingClient = new CapturingChatClient();
        ILlmPromptService service = new MockLlmPromptService(capturingClient);

        const string sanitized = "Customer <PERSON_1> with email <EMAIL_1>.";
        await service.SendPromptAsync(sanitized);

        capturingClient.LastUserMessage.Should().Be(sanitized);
        capturingClient.LastUserMessage.Should().NotContain("ravi.kumar@gmail.com");
        capturingClient.LastUserMessage.Should().NotContain("Ravi Kumar");
    }

    [Test]
    public async Task SendPromptAsync_AfterSanitization_OnlyPlaceholdersReachLlm()
    {
        var capturingClient = new CapturingChatClient();
        var sanitizer = ProductionPipelineFactory.Create().Sanitizer;
        ILlmPromptService service = new MockLlmPromptService(capturingClient);

        const string prompt = "Email ravi.kumar@gmail.com please.";
        var result = sanitizer.Sanitize(new SanitizationRequest(prompt));

        result.SanitizedPrompt.Should().Contain("<EMAIL_1>");
        await service.SendPromptAsync(result.SanitizedPrompt);

        capturingClient.LastUserMessage.Should().Contain("<EMAIL_1>");
        capturingClient.LastUserMessage.Should().NotContain("ravi.kumar@gmail.com");
    }

    [TestCase(null)]
    [TestCase("")]
    [TestCase("   ")]
    public void SendPromptAsync_InvalidSanitizedPrompt_ThrowsArgumentException(string? prompt)
    {
        ILlmPromptService service = new MockLlmPromptService(new MockChatClient());
        var action = async () => await service.SendPromptAsync(prompt!);
        action.Should().ThrowAsync<ArgumentException>();
    }
}