FakingDbContext.cs

public interface IPeopleContext : IDisposable, IEntitiesContext {

    IDbSet<Person> People { get; set; }
    IDbSet<Book> Books { get; set; }
}

public interface IEntitiesContext : IDisposable {

    DbEntityEntry<TEntity> Entry<TEntity>(TEntity entity) where TEntity : class;
    IDbSet<TEntity> Set<TEntity>() where TEntity : class;
    int SaveChanges();
}