Xunit - How to use Moq and EF Core for Identity Primary Key

Question

Xunit - How to use Moq and EF Core for Identity Primary Key

c# entity-framework-core moq xunit

Question

I am trying to automate my UnitTesting with AutoMoq and Xunit for Inserting feature.

But I keep getting that I cannot insert a value into the KeyColumn as the following. EnrolmentRecordID is the IdentityColumn in my SQL db and its value is generated automatically at the insertion.

Message: Microsoft.EntityFrameworkCore.DbUpdateException : An error occurred while updating the entries. See the inner exception for details. ---- System.Data.SqlClient.SqlException : Cannot insert explicit value for identity column in table 'EN_Schedules' when IDENTITY_INSERT is set to OFF.

It can be avoided, if I don't use Moq or I don't set the data to EnrolmentRecordID column. But I don't know how to exclude EnrolmentRecordID in AutoMoq. Since it's the key column, I cannot set the NULLABLE feature to that column too.

StudentSchedule.cs

public class StudentSchedule
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int EnrolmentRecordID { get; set; }

    public string AcademicYearID { get; set; }
    [Display(Name = "Student")]
    public string StudentName { get; set; }

    public string ProposedQual { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public DateTime? DateCreated { get; set; }
}

AddService

public async Task Add(StudentSchedule model)
{
    await _context.Schedules.AddAsync(model);
    await _context.SaveChangesAsync();
}

XUnitTest

public class TestCommandsSchedule
{
    private ERAppData.Commands.CommandSchedule _command;
    public TestCommandsSchedule()
    {
        _command = new ERAppData.Commands.CommandSchedule(AppsecDBContext.GenerateAppsecDBContext() as ERAppData.DbContexts.AppsecDbContext);
    }

    [Theory]
    [AutoMoqData]
    public async Task Should_Add_Schedule(StudentSchedule model)
    {            
        model.AcademicYearID = "16/17";
        model.DateCreated = null;

        await _command.Add(model);

        Assert.True(model.EnrolmentRecordID > 0);
    }
}

Could you please help me how I could use Moq to generate the MockObject and test the Add Service? Thanks.

TTCG

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Nkosi · Accepted Answer · 4/4/2017 2:33:47 PM

this simplified example shows how to decouple the subject under test from concretions so that it can be unit tested in isolation.

Abstract away the DbContext

public interface IStudenScheduleService : IGenericRepository<StudentSchedule> {
}

public interface IGenericRepository<T> {
    Task<T> AddAsync(T value, CancellationToken cancellationToken = default(CancellationToken));
    Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken));
}

making sure that the implementation wraps the actual context and provides desired functionality.

Have the subject class depend on the abstraction.

public class CommandSchedule {
    private readonly IStudenScheduleService _context;

    public CommandSchedule(IStudenScheduleService context) {
        this._context = context;
    }

    public async Task Add(StudentSchedule model) {
        await _context.AddAsync(model);
        await _context.SaveChangesAsync();
    }
}

With that in place the dependencies of the subject under test can be mocked and used in exercising the test.

[Theory]
[AutoMoqData]
public async Task Should_Add_Schedule(StudentSchedule model)  
   //Arrange
    var expectedId = 0;
    var expectedDate = DateTime.Now;

    var context = new Mock<IStudenScheduleService>();
    context.Setup(_ => _.SaveChangesAsync(It.IsAny<CancellationToken>()))
        .ReturnsAsync(1)
        .Callback(() => {
            model.EnrolmentRecordID = ++expectedId;
            model.DateCreated = expectedDate;
        })
        .Verifiable();

    context.Setup(_ => _.AddAsync(It.IsAny<StudentSchedule>(), It.IsAny<CancellationToken>()))
        .ReturnsAsync((StudentSchedule m, CancellationToken t) => m)
        .Verifiable();

    var _command = new CommandSchedule(context.Object);

    model.AcademicYearID = "16/17";
    model.DateCreated = null;

    //Act
    await _command.Add(model);

    //Assert
    context.Verify();
    Assert.AreEqual(expectedId, model.EnrolmentRecordID);
    Assert.AreEqual(expectedDate, model.DateCreated);
}

Xunit - How to use Moq and EF Core for Identity Primary Key

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