After inserting a single entity into the generic repository using Entity Framework, how do I check that it's been inserted correctly?

Question

I am testing my generic repository that I'm trying to use to store various entities using Entity Framework. I have a test to see if inserting an employee works:

[TestMethod]
public void TestInsertEmployee1()
{
    InitializeDatabase();
    EFEmployee testEmployee1 = initializeEmployee1();
    EFRepo.Insert<EFEmployee>(testEmployee1);
    // what goes here to check if testEmployee1 has been inserted correctly?
    // I was thinking of a asserting that a count aggregation method of the
    // database is 1, but I don't know how to do that.
}

This is how my generic repository looks:

public class EFEmployeeEntityRepository : IEFEmployeeEntityRepository
{
    private readonly IBusinessEntityContext _context;

    public EFEmployeeEntityRepository(IBusinessEntityContext context)
    {
        this._context = context;
    }


    public virtual IQueryable<TEntity> BeginQuery<TEntity>() where TEntity : EFBusinessEntity
    {
        return _context.Set<TEntity>();
    }

    public void Delete<TEntity>(TEntity entity) where TEntity : class, IBusinessEntity
    {
        try
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            _context.Set<TEntity>().Remove(entity);
            this._context.SaveChanges();
        }
        catch (DbEntityValidationException dbEx)
        {
            var msg = string.Empty;

            foreach (var validationErrors in dbEx.EntityValidationErrors)
            {
                foreach (var validationError in validationErrors.ValidationErrors)
                {
                    msg += Environment.NewLine + string.Format("Property: {0} Error: {1}",
                    validationError.PropertyName, validationError.ErrorMessage);
                }
            }
            var fail = new Exception(msg, dbEx);
            throw fail;
        }
    }

    public TEntity GetById<TEntity>(Guid id) where TEntity : class, IBusinessEntity
    {          
        return _context.Set<TEntity>().Find(id);            
    }

    public void Insert<TEntity>(TEntity entity) where TEntity : class, IBusinessEntity
    {
        try
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            _context.Set<TEntity>().Add(entity);
            this._context.SaveChanges();
        }
        catch (DbEntityValidationException dbEx)
        {
            var msg = string.Empty;

            foreach (var validationErrors in dbEx.EntityValidationErrors)
            {
                foreach (var validationError in validationErrors.ValidationErrors)
                {
                    msg += string.Format("Property: {0} Error: {1}",
                    validationError.PropertyName, validationError.ErrorMessage) + Environment.NewLine;
                }
            }

            var fail = new Exception(msg, dbEx);
            throw fail;
        }
    }

    public void Update<TEntity>(TEntity entity) where TEntity : class, IBusinessEntity
    {
        try
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            TEntity existing = _context.Set<TEntity>().Find(entity.Id);
            if (existing != null)
            {
                _context.Entry(existing).CurrentValues.SetValues(entity);
                this._context.SaveChanges();
            }
        }
        catch (DbEntityValidationException dbEx)
        {
            var msg = string.Empty;
            foreach (var validationErrors in dbEx.EntityValidationErrors)
            {
                foreach (var validationError in validationErrors.ValidationErrors)
                {
                    msg += Environment.NewLine + string.Format("Property: {0} Error: {1}",
                    validationError.PropertyName, validationError.ErrorMessage);
                }
            }
            var fail = new Exception(msg, dbEx);
            throw fail;
        }
    }
}

This is what my context class looks like:

public class EFEmployeeEntityModelContext : DbContext, IBusinessEntityContext
{
    public EFEmployeeEntityModelContext()
        : base("EFEmployeeEntityModelContext")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        var typesToRegister = Assembly.GetExecutingAssembly().GetTypes()
        .Where(type => !String.IsNullOrEmpty(type.Namespace))
        .Where(type => type.BaseType != null && type.BaseType.IsGenericType &&
        type.BaseType.GetGenericTypeDefinition() == typeof (EntityTypeConfiguration<>));
        foreach (var type in typesToRegister)
        {
            dynamic configurationInstance = Activator.CreateInstance(type);
            modelBuilder.Configurations.Add(configurationInstance);
        }

        modelBuilder.Entity<EFEmployee>().HasRequired(t => t.Office).WithMany(u => u.Employees).HasForeignKey(d => d.OfficeID);
        modelBuilder.Entity<EFEmployee>().HasMany(t => t.Managing).WithRequired(t => t.ReportingTo);
        modelBuilder.Entity<EFEmployee>().HasRequired(t => t.Identity).WithOptional(u => u.Employee);

        base.OnModelCreating(modelBuilder);
    }

    DbSet<TEntity> IBusinessEntityContext.Set<TEntity>()
    {
        return this.Set<TEntity>();
    }
}

Based on these classes, what can I use to check that insert works? Do I need a unit of work class? And do I need a service layer? Everything's so confusing. I don't even understand what's the difference between a DbContext and IDbSet<T>, or what a DbContext's .Set<T> is about, I've just been following tutorials to create my repositories and stuff.