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