llm-pii-poc/tests/PiiRedaction.Core.Tests/Redaction/PlaceholderPiiRedactorTests.cs

using FluentAssertions;
using PiiRedaction.Core.Models;
using PiiRedaction.Core.Redaction;

namespace PiiRedaction.Core.Tests.Redaction;

[TestFixture]
public sealed class PlaceholderPiiRedactorTests
{
    private readonly PlaceholderPiiRedactor _redactor = new();

    [Test]
    public void Redact_NoEntities_ReturnsOriginalTextAndEmptyMap()
    {
        const string text = "No PII here.";
        var result = _redactor.Redact(text, []);

        result.SanitizedText.Should().Be(text);
        result.PlaceholderMap.Should().BeEmpty();
    }

    [Test]
    public void Redact_SingleEntity_ReplacesWithTypedPlaceholder()
    {
        const string text = "Email ravi@test.com end.";
        var entities = new[] { Entity(PiiEntityType.Email, "ravi@test.com", 6) };

        var result = _redactor.Redact(text, entities);

        result.SanitizedText.Should().Be("Email <EMAIL_1> end.");
        result.PlaceholderMap["<EMAIL_1>"].Should().Be("ravi@test.com");
    }

    [Test]
    public void Redact_DuplicateSameTypeAndValue_ReusesPlaceholder()
    {
        const string text = "a@b.co and a@b.co";
        var entities = new[]
        {
            Entity(PiiEntityType.Email, "a@b.co", 0),
            Entity(PiiEntityType.Email, "a@b.co", 11)
        };

        var result = _redactor.Redact(text, entities);

        result.SanitizedText.Should().Be("<EMAIL_1> and <EMAIL_1>");
        result.PlaceholderMap.Should().HaveCount(1);
    }

    [Test]
    public void Redact_MultipleTypes_AssignsIndependentCounters()
    {
        const string text = "9876543210 ravi@test.com";
        var entities = new[]
        {
            Entity(PiiEntityType.Phone, "9876543210", 0),
            Entity(PiiEntityType.Email, "ravi@test.com", 11)
        };

        var result = _redactor.Redact(text, entities);

        result.SanitizedText.Should().Be("<PHONE_1> <EMAIL_1>");
    }

    [Test]
    public void Redact_MultipleSameTypeDifferentValues_IncrementsCounter()
    {
        const string text = "Customer Ravi Kumar and Customer Priya Nair";
        var entities = new[]
        {
            Entity(PiiEntityType.Person, "Ravi Kumar", 9),
            Entity(PiiEntityType.Person, "Priya Nair", 33)
        };

        var result = _redactor.Redact(text, entities);

        result.SanitizedText.Should().Be("Customer <PERSON_2> and Customer <PERSON_1>");
        result.PlaceholderMap.Should().HaveCount(2);
    }

    [Test]
    public void Redact_EntityTypes_UseTypedPlaceholderPrefixes()
    {
        (PiiEntityType Type, string Prefix)[] cases =
        [
            (PiiEntityType.Person, "PERSON"),
            (PiiEntityType.Email, "EMAIL"),
            (PiiEntityType.LoanNumber, "LOAN_NUMBER")
        ];

        foreach (var (type, prefix) in cases)
        {
            const string value = "VALUE";
            var text = $"start {value} end";
            var result = _redactor.Redact(text, [Entity(type, value, 6)]);
            result.SanitizedText.Should().Contain($"<{prefix}_1>", because: type.ToString());
        }
    }

    [Test]
    public void Redact_RightToLeftReplacement_PreservesCorrectOutput()
    {
        const string text = "AA BB CC";
        var entities = new[]
        {
            Entity(PiiEntityType.Phone, "AA", 0),
            Entity(PiiEntityType.Email, "BB", 3),
            Entity(PiiEntityType.Pan, "CC", 6)
        };

        var result = _redactor.Redact(text, entities);

        result.SanitizedText.Should().Be("<PHONE_1> <EMAIL_1> <PAN_1>");
    }

    [TestCase(null)]
    [TestCase("")]
    [TestCase("   ")]
    public void Redact_InvalidText_ThrowsArgumentException(string? text)
    {
        var action = () => _redactor.Redact(text!, []);
        action.Should().Throw<ArgumentException>();
    }

    [Test]
    public void Redact_NullEntities_ThrowsArgumentNullException()
    {
        var action = () => _redactor.Redact("text", null!);
        action.Should().Throw<ArgumentNullException>();
    }

    private static PiiEntity Entity(PiiEntityType type, string value, int start) =>
        new(type, value, start, value.Length, PiiDetectionSource.Regex);
}