CPPUnit how do I write a test? - c++

Question

Okay I basically want to get the ball rolling and write some CPPUnit tests but I have no idea how to go about it. Here I have some code that basically gets a pointer to the Menu Button for the associated button group and position arguments, how would I go about creating a test for this?
CMenuButton* CMenuContainer::GetButton(const enumButtonGroup argGroup, const int32_t argPosition)
{
CMenuButton* pButton = NULL;
if (argGroup < MAX_GROUP_BUTTONS)
{
pButton = m_ButtonGroupList[argGroup].GetButton(argPosition);
}
return pButton;
In reply to #Fabio Ceconello, would it be possible to set some tests for some code like this?
unsigned long CCRC32::Reflect(unsigned long ulReflect, const char cChar)
{
unsigned long ulValue = 0;
// Swap bit 0 for bit 7, bit 1 For bit 6, etc....
for(int iPos = 1; iPos < (cChar + 1); iPos++)
{
if(ulReflect & 1)
{
ulValue |= (1 << (cChar - iPos));
}
ulReflect >>= 1;
}
return ulValue;
}

Answer 1

CppUnit isn't well suited for creating automated tests for user interface. It's more for processing-only units. For instance, let's say you created a replacement for std::vector and want to make sure it behaves like the original one, you could write tests that add elements to both your and the standard implementation, then do some more handling (removing, changing elements, etc.) and after each step check if the two have a consistent result.
For UI I'm not aware of good open source/free tools, but one good commercial tool is TestComplete from Smart Bear, among others.
For the second example you gave, the first thing is to define a validity check for the Reflect() method. You can, for instance, calculate the result of some values by hand to check if the returned value for each of them is what was expected. Or you could use an inverse function that's known to be fully working.
Assuming the first option, you could write the test like this:
class CRC32Test : public CppUnit::TestCase
{
public:
CRC32Test( std::string name ) : CppUnit::TestCase( name ) {}
void runTest()
{
struct Sample {unsigned long ulReflect; char cChar; unsigned long result};
static Sample samples[] =
{
// Put here the pre-calculated values
};
int count = sizeof(samples) / sizeof(Sample);
for (int i = 0; i < count; ++i)
CPPUNIT_ASSERT(subject.Reflect(samples[i].ulReflect, samples[i].cChar) == samples[i].result);
}
private:
CRC32 subject;
};
int main(void)
{
CppUnit::TextUi::TestRunner runner;
runner.addTest(new CppUnit::TestCaller<CRC32Test>("test CRC32", &CRC32::runTest));
runner.run();
}