Untitled

using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;
using Microsoft.Xrm.Sdk;
using System.Collections.Generic;

// Assuming your original method is in a class named MyDataService
[TestClass]
public class MyDataServiceTests
{
    [TestMethod]
    public void RetrieveContactFromSystemUser_ShouldReturnContactForValidSystemUserId()
    {
        // Arrange
        Guid validSystemUserId = Guid.NewGuid();
        var serviceMock = new Mock<IOrganizationService>();

        // Setup a mock response for the RetrieveMultiple method
        var contactEntity = new Entity("contact");
        contactEntity.Attributes["fullname"] = "John Doe";
        contactEntity.Attributes["contactid"] = Guid.NewGuid();
        var entityCollection = new EntityCollection(new List<Entity> { contactEntity });

        serviceMock.Setup(service => service.RetrieveMultiple(It.IsAny<QueryExpression>()))
                   .Returns(entityCollection);

        var myDataService = new MyDataService(); // Create an instance of your service

        // Act
        var result = myDataService.RetrieveContactFromSystemUser(serviceMock.Object, validSystemUserId);

        // Assert
        Assert.IsNotNull(result);
        Assert.AreEqual("John Doe", result.GetAttributeValue<string>("fullname"));
        // Add more assertions based on your specific requirements and expected data
    }

    [TestMethod]
    public void RetrieveContactFromSystemUser_ShouldReturnNullForInvalidSystemUserId()
    {
        // Arrange
        Guid invalidSystemUserId = Guid.NewGuid();
        var serviceMock = new Mock<IOrganizationService>();

        // Setup a mock response for the RetrieveMultiple method (empty collection)
        serviceMock.Setup(service => service.RetrieveMultiple(It.IsAny<QueryExpression>()))
                   .Returns(new EntityCollection());

        var myDataService = new MyDataService(); // Create an instance of your service

        // Act
        var result = myDataService.RetrieveContactFromSystemUser(serviceMock.Object, invalidSystemUserId);

        // Assert
        Assert.IsNull(result);
    }
}