I am very new to unit testing and I am a little confused.
I am trying to do unit testing (using the Boost unit testing framework) on a C++ class called VariableImpl
. Here are the details.
class Variable
{
public:
void UpdateStatistics (void) {
// compute mean based on m_val and update m_mean;
OtherClass::SendData (m_mean);
m_val.clear ();
}
virtual void RecordData (double) = 0;
protected:
std::vector<double> m_val;
private:
double m_mean;
};
class VariableImpl : public Variable
{
public:
virtual void RecordData (double d) {
// put data in m_val
}
};
My question is how can I check that the mean is computed correctly? Note that 1) m_mean
is protected and 2) UpdateStatistics
calls a method of another class and then clears the vector.
The only way I can see would be to add a getter (for instance, GetMean
), but I don't like this solution at all, nor I think it is the most elegant.
How should I do?
And what should I do if I were to test a private method instead of a private variable?
TIA,
Jir
Well, unit testing should test units and ideally every class is a self-contained unit – this follows directly from the single responsibility principle.
So testing private members of a class shouldn’t be necessary – the class is a black box that can be covered in a unit test as-is.
On the other hand, this isn’t always true, and sometimes with good reasons (for instance, several methods of the class could rely on a private utility function that should be tested). One very simple, very crufty but ultimately successful solution is to put the following into your unit-test file, before including the header that defines your class:
#define private public
Of course, this destroys encapsulation and is evil. But for testing, it serves the purpose.