How to write unittest for database classes?

Question

public bool insertCustomer(Customer newCustomer)
  {
bool inserted =false;
SqlCommand cmd=new SqlCommand();
cmd.CommandText= "insert into Customer (name, firstname, address) values (@name, @firstname, @address)";
cmd.Parameters.add(new SqlParameter("@name",Customer.name));
cmd.Parameters.add(new SqlParameter("@firstname",Customer.firstname));
cmd.Parameters.add(new SqlParameter("@address",Customer.address));

// executes command here and it returns new ID  isnsterted= true;

return inserted ;
  }