Testing Example

The purpose of the demonstration program PassStatsBasic is to input a csv file of gender and percentage for exam results of a group of students and to output the pass rate (expressed as a percentage) for males and females. Make sure that you can understand the code before moving on to program PassStats, which includes plenty of validation in an attempt to make it robust.

program PassStatsBasic;
  {$APPTYPE CONSOLE}
  //Reads scores for males and females from a csv file
  //and outputs pass rate for each.
uses
  SysUtils, Strutils;
const
  FILE_NAME = 'marksheet.csv';
  PASSMARK = 40;
var
  intCurrentScore, intMales, intFemales, intMalePasses, intFemalePasses : integer;
  strCurrentScore, strMalePassRate, strFemalepassRate : string;
  charCurrentGender : char;
  rMalePassRate, rFemalePassRate : real;

procedure CalcStats(FileName : string);
var
  Marks : Text;
  strCurrentLine : string;
  ErrorCode : integer;
begin
  intMales := 0;
  intFemales := 0;
  intMalePasses := 0;
  intFemalepasses := 0;
  intCurrentScore := 0;
  assignFile(Marks, FileName);
  reset(Marks);
  while not eof(Marks) do
    begin
      readln(Marks, strCurrentLine);
      charCurrentGender := LeftStr(strCurrentLine, 1)[1];
      charCurrentGender :=  UpCase(charCurrentGender);
      strCurrentScore := rightStr(strCurrentLine, length(strCurrentLine) - 2);
      val(strCurrentScore, intCurrentScore, ErrorCode);
      if charCurrentGender = 'M' then
        begin
          inc(intMales);
          if intCurrentscore >= PASSMARK then
            inc(intMalePasses);
         end
      else //females
        begin
          inc(intFemales);
          if intCurrentscore >= PASSMARK then
            inc(intFemalePasses);
        end;
    end;
  closeFile(Marks);
  if intMales = 0 then
    begin
      writeln('No males');
      strMalePassRate := 'NoMales';
    end
  else
    begin
      rMalePassRate := intMalePasses * 100 / intMales;
      strMalePassRate := FloatToStrf(rMalePassRate, ffFixed, 6, 2);
    end;
  if intFemales = 0 then
    begin
      writeln('No females');
      strFemalePassRate := 'NoFemales';
    end
  else
    begin
      rFemalePassRate := intFemalePasses * 100 / intFemales;
      strFemalePassRate := FloatToStrf(rFemalePassRate, ffFixed, 6, 2);
    end;
  writeln('Male Pass Rate (%): ', strMalePassRate);
  writeln('Female Pass Rate (%): ', strFemalePassRate);
end;

begin
  CalcStats(FILE_NAME);
  readln;
end.

The validated version of the program should be able to handle blank lines or lone commas in the csv file, report a missing data file, and reject files with erroneous data. It should accept groups of a single gender and calculate percentages correct to two places of decimals. We use the description lone comma to refer to a line containing only a comma. (The data in the csv file is likely to have originated in a spreadsheet, and a blank line will convert to a lone comma).

program PassStats;
{$APPTYPE CONSOLE}
 //Reads scores for males and females from a csv file
 //and outputs pass rate for each.
uses
  SysUtils, Strutils;
const
  PASSMARK = 40;
  ERROR_MESSAGES : array [0..6] of string = ('',
                                            'File not found',
                                            'File empty',
                                            'Comma should follow letter.',
                                            'First letter must be M or F.',
                                            'Mark must be between 0 and 100 inclusive.',
                                            'An integer must be after the comma.');

var
  intCurrentScore, intMales, intFemales, intMalePasses, intFemalePasses, intLine, intError : integer;
  strCurrentScore : string;
  charCurrentGender : char;
  rMalePassRate, rFemalePassRate : real;
  ErrorFound : Boolean;

procedure OutPutError(var intError : integer);
begin
  ErrorFound := True;
  write(ERROR_MESSAGES[intError]);
  if intLine = 0 then
    writeln
  else
    writeln(' at line ', intLine);
end;

procedure CalcStats(FileName : string);
var
  Marks : Text;
  strCurrentLine :  string;
  CommaPos : integer;
  ErrorCode : integer;
begin
  intError := 0;
  intLine := 0;
  if not fileExists(FileName) then
    begin
      OutPutError(1);
    end
  else
    begin
      intMales := 0;
      intFemales := 0;
      intMalePasses := 0;
      intFemalepasses := 0;
      intCurrentScore := 0;
      ErrorFound := False;

      assignFile(Marks, FileName);
      reset(Marks);
      if eof(Marks) then
        OutPutError(2)
      else
        begin
          while not eof(Marks) do
            begin
              repeat
                readln(Marks, strCurrentLine);
                inc(intLine);
              until (strCurrentLine <> ',') or eof(Marks);
              CommaPos := pos(',', strCurrentline);
              if (CommaPos <> 2) and (strCurrentLine <> ',') then
                OutputError(3)
              else
                begin
                  charCurrentGender := LeftStr(strCurrentLine, 1)[1];
                  charCurrentGender :=  UpCase(charCurrentGender);
                  if not (charCurrentGender in ['M', 'F']) then
                    begin
                     OutputError(4)
                  else
                    begin
                      strCurrentScore := rightStr(strCurrentLine, length(strCurrentLine) - 2);
                      val(strCurrentScore, intCurrentScore, ErrorCode);
                      if not (ErrorCode = 0) then
                        OutPutError(6)
                      else
                        begin
                          if (intCurrentScore < 0) or (intCurrentScore > 100) then
                            begin
                              OutPutError(5);
                            end
                          else  //no error detected
                            begin
                              if charCurrentGender = 'M' then
                                begin
                                  inc(intMales);
                                  if intCurrentscore >= PASSMARK then
                                    inc(intMalePasses);
                                end
                              else //females
                                begin
                                  inc(intFemales);
                                  if intCurrentscore >= PASSMARK then
                                    inc(intFemalePasses);
                                end;
                            end; //if (intCurrentScore < 0) or (intCurrentScore > 100)
                       end; //if not (ErrorCode = 0)
                    end; //if not (charCurrentGender in ['M', 'F'])
                end; //if CommaPos <> 2
            end; //while
            closeFile(Marks);
            if not ErrorFound then
              begin
                if intMales = 0 then
                  begin
                    writeln('No males');
                    strMalePassRate := 'NoMales';
                  end
                else
                  begin
                    rMalePassRate := intMalePasses * 100 / intMales;
                    strMalePassRate := FloatToStrf(rMalePassRate, ffFixed, 6, 2);
                    writeln('Male Pass Rate (%): ', strMalePassRate);
                  end;
                if intFemales = 0 then
                  begin
                    writeln('No females');
                    strFemalePassRate := 'NoFemales';
                  end
                else
                  begin
                    rFemalePassRate := intFemalePasses * 100 / intFemales;
                    strFemalePassRate := FloatToStrf(rFemalePassRate, ffFixed, 6, 2);
                    writeln('Female Pass Rate (%): ', strFemalePassRate);
                  end;
              end; //if not ErrorFound
        end; //if eof(Marks)
    end; //if not fileExists(FileName)
end;

begin
  CalcStats('marksheet.csv');
  readln;
end.

Black box testing is a form of testing that is performed without reference to the source code. We can input examples of normal, borderline/boundary/extreme and erroneous data regardless of how the code is written. We tabulate below our test plan (columns 1-6) with results (column 7). We produced t7.csv by using the data generator at generatedata.com. Rather than provide the evidence in the form of seven screenshots here, we show the neat output of automated testing in the following two sections.

For your convenience, we have put the test files and the source code of this tutorial's programs into testing.zip.

You may have thought of additional test cases for black box testing, such as various combinations of symbols. Please let us know if you discover test cases that reveal errors in this program. For commercial applications there will be time and budget considerations, and choices must be made about the test cases most likely to uncover a fault. For small programs of your own, it is more likely to be a question of how many tests you can be bothered to do! (Even after extensive testing, a program cannot be guaranteed to be bug-free).