From: Travis Whitton <whitton@...>
Date: 2003-01-17T02:22:16+09:00
Subject: Unit Testing in dynamic environments

I'm just starting to get into unit testing, and I can already see how powerful
a tool it can be to preemptively find bugs in my programs; however, a good
portion of the classes I write revolve around databases and CGI. A lot of the
methods implemented in these classes return highly variable results. Is there
a way for me to leverge the benefits of unit testing when working with this
type of data? Here's an excerpt of a typical class I might write:

class DB
  def initialize()
    @lims = nil # LIMS system
    lims_connect
  end

  def lims_connect
    @lims = DBI.connect("DBI:Mysql:somedb", "someuser", "somepass")
    @lims.connected?
  end

  def get_pct_solids(sample_number)
   samp = sample_number.scan(/\d{6}/).to_s

    sql = "select SA_RESULT from sample where SA_SAMPNO = '#{samp}'
           and SA_ANAABB = '%SOLIDS' and (SA_STATUS = 'E' or SA_STATUS = 'F')"
    @lims.prepare(sql) do |sth|
      sth.execute

      if sth.rows > 0
        last_pct_solids = sth.fetch.to_s.to_f
        last_pct_solids /= 100.0 # Must force float
        sth.finish
        return last_pct_solids
      else
        sth.finish
        return false
      end
    end
  end
end

Would there be a way to use unit test my get_pct_solids method, or is it only
suited for environments where functions return predictable values?

Thanks,
Travis Whitton <whitton@atlantic.net>