llm-pii-poc/tests/PiiRedaction.Core.Tests/Detection/RegexPiiDetectorTests.cs

using FluentAssertions;
using PiiRedaction.Core.Detection;
using PiiRedaction.Core.Models;

namespace PiiRedaction.Core.Tests.Detection;

[TestFixture]
public sealed class RegexPiiDetectorTests
{
    private readonly RegexPiiDetector _detector = new();

    [Test]
    public void Detect_PositiveEmail_ReturnsEntity()
    {
        const string text = "Contact ravi.kumar@gmail.com now.";
        var entities = _detector.Detect(text);

        entities.Should().ContainSingle(entity =>
            entity.Type == PiiEntityType.Email &&
            entity.Value == "ravi.kumar@gmail.com" &&
            entity.Source == PiiDetectionSource.Regex);
    }

    [Test]
    public void Detect_PositivePhone_ReturnsTenDigitEntity()
    {
        var entities = _detector.Detect("Call 9876543210 today.");

        entities.Should().ContainSingle(entity =>
            entity.Type == PiiEntityType.Phone &&
            entity.Value == "9876543210" &&
            entity.Source == PiiDetectionSource.Regex);
    }

    [TestCase("Aadhaar 1234 5678 9012 linked.", "1234 5678 9012")]
    [TestCase("Aadhaar 123456789012 linked.", "123456789012")]
    public void Detect_PositiveAadhaar_ReturnsEntity(string text, string expectedValue)
    {
        var entities = _detector.Detect(text);

        entities.Should().ContainSingle(entity =>
            entity.Type == PiiEntityType.Aadhaar &&
            entity.Value == expectedValue);
    }

    [Test]
    public void Detect_PositivePan_ReturnsUppercaseEntity()
    {
        var entities = _detector.Detect("PAN ABCDE1234F verified.");

        entities.Should().ContainSingle(entity => entity.Type == PiiEntityType.Pan);
        entities[0].Value.Should().MatchRegex("^[A-Z]{5}\\d{4}[A-Z]$");
    }

    [Test]
    public void Detect_PositiveCreditCard_ReturnsEntity()
    {
        var entities = _detector.Detect("Card 4111-1111-1111-1111 used.");

        entities.Should().ContainSingle(entity => entity.Type == PiiEntityType.CreditCard);
    }

    [TestCase("not-an-email")]
    [TestCase("@missing.com")]
    [TestCase("pan abcde1234f")]
    [TestCase("Number 987654321")]
    public void Detect_NegativePatterns_ReturnsNoMatch(string text)
    {
        _detector.Detect(text).Should().BeEmpty();
    }

    [Test]
    public void Detect_EmailSpan_HasCorrectIndices()
    {
        const string text = "Email ravi@test.com end.";
        var entities = _detector.Detect(text);

        var email = entities.Single(entity => entity.Type == PiiEntityType.Email);
        email.StartIndex.Should().Be(6);
        email.Length.Should().Be("ravi@test.com".Length);
        text[email.StartIndex..email.EndIndex].Should().Be("ravi@test.com");
    }

    [TestCase(null)]
    [TestCase("")]
    [TestCase("   ")]
    public void Detect_InvalidInput_ThrowsArgumentException(string? text)
    {
        var action = () => _detector.Detect(text!);
        action.Should().Throw<ArgumentException>();
    }
}