A little test harness for Lua

Purpose: show a simple way to create and run simple testsuites. Yes, the keyword is "simple"...

The code in "tester.lua" is shown below, but first... an example:

  dofile('tester.lua')
  tester [[
    1
    1+1
    getn(globals())
    tinsert(globals(),"abc")
    getn(globals())
    tremove(globals())
    getn(globals())
  ]]

The output of this code is:

                                   1 == 1
                                 1+1 == 2
                     getn(globals()) == 0
            tinsert(globals(),"abc") == userdata, tag = 0
                     getn(globals()) == 1
                  tremove(globals()) == abc
                     getn(globals()) == 0

What happens is that each line gets evaluated and printed alongside its result.

Once you have your tests working, you may want to consider turning this into a regression test. That's easy - take the above output and create this script from it:

  dofile('tester.lua')
  tester [[
                                   1 == 1
                                 1+1 == 2
                     getn(globals()) == 0
            tinsert(globals(),"abc") == userdata, tag = 0
                     getn(globals()) == 1
                  tremove(globals()) == abc
                     getn(globals()) == 0
  ]]

When you run the above script, it will generate no output - how's that for a time saver!

But wait, what if there are errors? Try this:

  dofile('tester.lua')
  tester [[
                                   1 == 1
                                 1+1 == 1
                                 1+1 == 2
                     getn(globals()) == 1
                     getn(globals()) == 0
  ]]

The output will be:

                                 1+1 == 2
                     getn(globals()) == 0
 3 results out of 5 matched

FWIW, this little test harness was inspired by a test system for Python, written by Tim Peters.

Here is the "tester.lua" script needed to run the above examples:

  #!/usr/bin/env lua

  -- a little test harness for Lua scripts
  -- 09/02/2001 jcw@equi4.com

  -- evaluate each line in turn, optionally comparing results
  -- if a comparison is included and it matches, nil is returned
  -- otherwise, output is such that it can be re-used as match input
  function tester(lines)
    local t={}
    gsub(lines,"\n*([^\n]+)\n*", function (v) tinsert(%t,v) end)
    local f = function (s,t)
      local r=dostring('return '..s)
      if type(r)=="nil" then
        r="nil"
      elseif type(r)=="number" then
        r=r..""
      elseif type(r)=="table" then
        r='table, n = '..getn(r)..', tag = '..tag(r)
      elseif type(r)=="userdata" then
        r='userdata, tag = '..tag(r)
      elseif type(r)=="function" then
        r=type(r)
      end
      if r~=t then return format('%36s == %s',s,r) end
    end
    local m,c=0,0
    for i=1,getn(t) do
      local l=gsub(gsub(t[i],'^ +',''),' +$','')
      if i==getn(t) and l=="" then break end
      if strfind(l,' == ') then
        c=c+1
        local o=gsub(l,'^(.*) == (.*)$',f,1)
        if o~="" then print(o) else m=m+1 end
      else
        print(f(l))
      end
    end
    if m<c then print(m..' results out of '..c..' matched') end
  end