def test_changes
      @db.execute("create table foo ( a integer primary key, b integer )")
      assert_equal 0, @db.changes
      @db.execute("insert into foo (b) VALUES (1)")
      assert_equal 1, @db.changes
      @db.execute("update foo set b = b + ? where b = ?", [2, 1])
      assert_equal 1, @db.changes
      assert_equal [[3]], @db.execute("select b from foo")
    end