Re: Is this kind of static polymorphism valid?

From:
Casey Carter <Casey_at_Carter_dot_net@dontspam.me.invalid>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 5 Sep 2012 21:22:36 -0700 (PDT)
Message-ID:
<k292kl$tfg$1@dont-email.me>
On 2012-09-05 17:02, DeMarcus wrote:

What I want to do is an ultra-light (syntax-wise) yet powerful TDD
framework. It looks like the following. It should compile but it's
possible that the self-registering doesn't run perfectly due to the
initialization order thing. This is just to show you the idea.


[snip code]

Also another question I have is why I can't put the specialized
runTests() function within the unnamed namespace as well? I get the
following error from gcc 4.7.1.


runTests() must be defined in the namespace where it was declared,
i.e., the same namespace as MyTestFixture<T>.

I don't see what benefit your approach has over plain-old polymorphism
like:

// ITestFixture.hpp
#pragma once
class ITestFixture
{
public:
       static std::vector<ITestFixture*> testFixtures;

       virtual ~ITestFixture() {}
       virtual void runAllTests() = 0;
};

// MyTestFixture.hpp
#pragma once
#include <vector>
#include <string>
#include <functional>
#include <iostream>
#include "ITestFixture.hpp"

class MyTestFixture : public ITestFixture
{
public:
       MyTestFixture( const std::string& name )
       {
          // This is a self-registering object.
          testFixtures.push_back( this );
          std::cout << "Registering: " << name << std::endl;
       }

protected:
       void test( std::function<void()> function )
       {
          function();
       }
};

// FreeFunctions1Test.cpp
// !!! NOTE, it's a CPP file !!!
//
// This file will be multiplied and specialized for all the
// different unit tests.
#include "MyTestFixture.hpp"

namespace
{
class FreeFunctionTestFixture : public MyTestFixture
{
public:
       FreeFunctionTestFixture() : MyTestFixture( "Free Functions 1" )
       {}

private:
       void runAllTests()
       {
            test(
      [&]
               {
                  std::cout << "Test 1 for Free Functions 1" << std::endl;
               });

            test(
      [&]
               {
                  std::cout << "Test 2 for Free Functions 1" << std::endl;
               });
       }
};
FreeFunctionTestFixture tst;
}

// main.cpp
#include <vector>

#include "ITestFixture.hpp"

std::vector<ITestFixture*> ITestFixture::testFixtures;

int main()
{
       for( auto fixture : testFixtures )
          fixture->runAllTests();

       return 0;
}

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