Testing services in unit test repository pattern entity framework code first

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C#

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CodeFirst

Unity

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I'm trying to setup Unit Test in services using Moq and
NUnit I tried Mocking context and DbSet like

var mockSet = new Mock<DbSet<Student>>();
var mockContext = new Mock<Context>();
mockContext.SetupGet(m => m.Student).Returns(mockSet.Object);

but my services depends on other service so I tried [Setup] in TestInit Method but when I'm trying to test service I'm getting an exception "invalid setup on a non-virtual (overridable in VB) member: m => m.Student""
I need a solution to register my services and unity in unit test

What I have tried:

//this is how my whole code looks like
   [TestClass]
    public class StudentServiceTest
    {
        private IComService _mockComService;
        private IAccountService _mockAccountService;
       
        protected MRContext Context;

        private IUnitOfWork _mockUnitWork;

        [SetUp]
        public void TestInit(MRContext context, IAccountService accountService, IComService comService, IUnitOfWork unitOfWork)
        {
            
            this._mockComService = comService;
            _mockUnitWork = unitOfWork;
            this._mockAccountService = accountService;
            Context = context;

        }

        [TestInitialize]
        public void Initialize()
        {

            var mockSet = new Mock<DbSet<Student>>();
            var mockContext = new Mock<Context>();
            mockContext.SetupGet(m => m.Student).Returns(mockSet.Object);


           
        }


        [TestMethod]
        public void AutoAssignmentCases()
        {

            var service = new StudentService(_mockAccountService, _mockComService, _mockUnitWork);
            var students = service.DoSomeTask();
            Microsoft.VisualStudio.TestTools.UnitTesting.Assert.IsFalse(students.Any(c => !c.SubjectId.HasValue));
        }
    }