Make the Set entity framework method usable in unit tests

gistfile1.txt

/// <summary>
/// Overload of the Set method of entity framework
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public IDbSet<T> Set<T>() where T : class
{
    var correspondingDbSets = this.GetType().GetProperties().Where(a => a.PropertyType == typeof(IDbSet<T>));
    
    if (correspondingDbSets.Count() == 1)
    {
        var correspondingProperty = correspondingDbSets.FirstOrDefault();
        return (IDbSet<T>)correspondingProperty.GetValue(this,null);
    }
    throw new Exception("Unexisting dbset");
}