Two versions of a unit with different $DEFINEs in the same project

[Dmitry Onoshko 0]

I guess, I know the answer but maybe I miss something. The question arose related to unit testing with DUnitX but is not really tied to it.

 

Say, we have a Delphi unit shared between multiple projects in a project group, and certain code pieces in the unit are written in $IFDEFs to exclude them in one of the projects and include for the rest (say, for performance reasons or to remove some stuff in a program for outside world use). The code pieces in question are part of quite complex algorithm(s), so unit testing is a must. I understand one can just create another build configuration for the DUnitX project, or even create a separate test project, but that’s not quite convenient: being able to test the whole unit in all its variant with a single test project would be much better.

 

Another use case I can imagine is something related to supporting different versions of some protocol or format in the same executable without the risk of introducing bugs by merging several implementations into a single one (although this could probably be done by giving unit for different versions different names). So, let’s just stick to testing $IFDEF-dependent unit as a whole in one test project as the use case.

 

I guess, linker and separate unit compilation are one of the problems here, but… Is that even possible?

[dummzeuch 1664]

You could use includes from different units for testing.

 

Lets say this is the unit you want to test:

{$IFNDEF UNIT_TESTING}
unit ToTest;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;
function NotAlwaysAvaialble(): TSomeOtherType;

implementation

uses
  Other,
  Units;

{$ENDIF}

function AlwaysAvailable(): TSomeType;
begin
  // implementation here
end;

{$IFDEF USE_EVERYTHING}
function NotAlwaysAvaialble(): TSomeOtherType;
begin
  // implementation here
end;
{$ENDIF}

{$IFNDEF UNIT_TESTING}
end.
{$ENDIF}

Instead of directly using this unit in the unit tests, you use two (or more) different units that include that unit, e.g.:

unit UnitForTesting1;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;
function NotAlwaysAvaialble(): TSomeOtherType;

implementation

uses
  Other,
  Units;

implementation

{$DEFINE UNIT_TESTING}
{$DEFINE USE_EVERYTHING}
{$I 'ToTest'}

end.

and

unit UnitForTesting2;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;

implementation

uses
  Other,
  Units;

implementation

{$DEFINE UNIT_TESTING}
{$I 'ToTest'}

end.

I haven't tested this, but it should work.

On the other hand, this makes the testing code quite confusing and might lead to code not being tested as intended.

[Dmitry Onoshko 0]

2 minutes ago, dummzeuch said:

You could use includes from different units for testing.

 

Lets say this is the unit you want to test:

{$IFNDEF UNIT_TESTING}
unit ToTest;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;
function NotAlwaysAvaialble(): TSomeOtherType;

implementation

uses
  Other,
  Units;

{$ENDIF}

function AlwaysAvailable(): TSomeType;
begin
  // implementation here
end;

{$IFDEF USE_EVERYTHING}
function NotAlwaysAvaialble(): TSomeOtherType;
begin
  // implementation here
end;
{$ENDIF}

{$IFNDEF UNIT_TESTING}
end.
{$ENDIF}

Instead of directly using this unit in the unit tests, you use two (or more) different units that include that unit, e.g.:

unit UnitForTesting1;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;
function NotAlwaysAvaialble(): TSomeOtherType;

implementation

uses
  Other,
  Units;

implementation

{$DEFINE UNIT_TESTING}
{$DEFINE USE_EVERYTHING}
{$I 'ToTest'}

end.

and

unit UnitForTesting2;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;

implementation

uses
  Other,
  Units;

implementation

{$DEFINE UNIT_TESTING}
{$I 'ToTest'}

end.

I haven't tested this, but it should work.

On the other hand, this makes the testing code quite confusing and might lead to code not being tested as intended.

I feel $INCLUDEing full units in an implementation section might not work, but I think I get the idea. And I’d agree with you that this would make it trickier than it should as the unit should have been torn into pieces for $INCLUDEing, all that only to test it.

[Rollo62 595]

I like to separate different aspects of stuff in completely different units, which where combined then in a wrapper unit, like so

unit DecideWhichUnitInPlace;

interface

uses
// This is the only place where separation takes place 
{$IFDEF UNIT_TESTING}
  UnitWithTests,
{$ELSE              }
  UnitWithoutTests
{$ENDIF             }
  ;

//Even separate classes and interfaces like that, not only functions
type
// This can point to completely different, but cleanly separated versions, depending on defines
{$IFDEF UNIT_TESTING}
    TMyType = UnitWithTests.TMyType;
{$ELSE              }
    TMyType = UnitWithoutTests.TMyType;
{$ENDIF             }
    ;



implementation

Then no defines are needed in those units at all

unit UnitWithTest;

interface

uses
  Whateever,
  isNecesssary;

function AlwaysAvailable(): TSomeType;
function NotAlwaysAvaialble(): TSomeOtherType;

type
  TMyType = class
    function AlwaysAvailable(): TSomeType;
    function NotAlwaysAvaialble(): TSomeOtherType;  
  end

implementation

uses
  Other,
  Units;

function AlwaysAvailable(): TSomeType;
begin
  // implementation here
end;

function NotAlwaysAvaialble(): TSomeOtherType;
begin
  // implementation here
end;


function TMyType.AlwaysAvailable(): TSomeType;
begin
  // call
  AlwaysAvailable;
end;

function TMyType.NotAlwaysAvaialble(): TSomeOtherType;
begin
  // call
  NotAlwaysAvaialble;
end;

end.

This is not the beest example to explain this and it depends highly on what you really want to achieve.
Maybe it gives you some helpful thoughts.

 

unit UnitWithoutTest;

interface

uses
  Whateever;

function AlwaysAvailable(): TSomeType;
//function NotAlwaysAvaialble(): TSomeOtherType;

type
  TMyType = class
    function AlwaysAvailable(): TSomeType;
    function NotAlwaysAvaialble(): TSomeOtherType;  
  end

implementation

uses
  Other,
  Units;

function AlwaysAvailable(): TSomeType;
begin
  // implementation here
end;

//function NotAlwaysAvaialble(): TSomeOtherType;
//begin
//  // NO implementation here, or completely removed
//end;


function TMyType.AlwaysAvailable(): TSomeType;
begin
  // call
  AlwaysAvailable;
end;

function TMyType.NotAlwaysAvaialble(): TSomeOtherType;
begin
  // call, ignore or mock, when function is NOT available
  //NotAlwaysAvaialble;
end;

 

[dummzeuch 1664]

14 hours ago, Dmitry Onoshko said:

I feel $INCLUDEing full units in an implementation section might not work, but I think I get the idea.

Including a full unit will definitely work, as long as it contains ifdefs that hide parts of it from the compiler. I have used this trick for many years to create pseudo templates long before Delphi had generics. The linked blog post explains it in depth.