Re: Is it a bad idea to define private: as public: ?
Am 25.08.2013 14:43, schrieb DeMarcus:
In books about TDD I've seen various solutions to do White-Box
testing, i.e. test the protected and private parts of classes.
I came up with an idea that if you do the following it would be easy
to test the internal parts of a class.
#define protected public
#define private public
Don't follow this dark path, Luke.
1) Doing so is undefined behaviour as of [macro.names] p2:
"A translation unit shall not #define or #undef names lexically
identical to keywords, to the identifiers listed in Table 3, or to the
attribute-tokens described in 7.6."
2) Even more so in the concrete example you present it also easily (if
not always in a realistic program) violates the one-definition rule (3.2
p6) as part of the core language, because there are two different
definitions of class PrintClass present in the program.
3) As of C++11 doing so has the potential to influence overload
resolution of function template, because access checking is now part of
the template substitution process.
Here's an example that compiles with gcc 4.7.2.
// PrintClass.h
#include <string>
class PrintClass
{
public:
std::string print() { return "Printing"; }
private:
std::string privatePrinting() { return "Printing private"; }
};
// main.cpp
#include <iostream>
#define protected public
#define private public
#include "PrintClass.h"
void whiteBoxTest()
{
PrintClass pc;
std::cout << pc.privatePrinting() << std::endl;
}
int main()
{
whiteBoxTest();
return 0;
}
My question is: is this a bad idea?
Yes indeed, see above why.
I can't really see the bad consequences but I guess things like SFINAE
could break.
Indeed.
They are much easier way to realize white box testing: Just declare a
Test class as friend, e.g.
#include <string>
class PrintClass
{
public:
std::string print() { return "Printing"; }
private:
std::string privatePrinting() { return "Printing private"; }
friend class Tester;
};
// main.cpp
#include <iostream>
#include "PrintClass.h"
struct Tester {
static std::string privatePrinting(PrintClass& pc)
{
return pc.privatePrinting();
}
};
void whiteBoxTest()
{
PrintClass pc;
std::cout << Tester::privatePrinting(pc) << std::endl;
}
int main()
{
whiteBoxTest();
return 0;
}
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