Testing an Overloaded Stream Operator

[tjlusco]

Hey guys, I'm wondering if there is a way to have access to the buffers used within cout/cin such that I can verify that overloaded stream operators are working correctly. The class I'm working with is a complex number class (CCmplxNum) which has the operators implemented.

std::istream &operator>>(std::istream &s, CCmplxNum &oZ);
std::ostream &operator<<(std::ostream &s, const CCmplxNum &oZ);

To give you an example of what I mean:

CCmplxNum oZ(1,1); // Create a complex num 1+1i
cout << oZ; // Displays complex number, "1+1i"
cin >> oZ; // User inputs a complex number

So I need a way of checking what is displayed to screen, and specifying what input is expected.

My guess is to create a seperate I/O stream (istream/ostream), and read the data that is placed into the ostream by the << operator. And to test the >> operator, place data into the istream, call the >> operator, and then check the oZ was updated correctly. I.e

istream inStream;
ostream outStream;
CCmplxNum oZ(1,1);
string strTest;

outStream << oZ; // Put oZ into the ostream
strTest = outStream.Something?; // ostream doesnt have any accessor methods
if (strTest == "1+1i"); // Testing

strTest = "1+1i"; // Test Input
inStream << strTest; // Somehow put the data into the stream
inStream >> oZ; // Test the extraction operator

The only problem is istream/ostream dont allow reading/writing to them, so you have no way of manipulating their buffers. Could anyone point me in the right direction?

Cheers, TjLusco

[Disch]

So I need a way of checking what is displayed to screen, and specifying what input is expected.

Am I missing something? Why can't you just use cin/cout and see what is put on the screen?


EDIT:

although I suppose if you want to check it programmatically you can use a stringstream:

#include <sstream>

//...

stringstream test;
test.str("5+3i");

test >> foo;
if( /*check foo here*/ )
  //...

test.str("");
foo = Foo(2,7);
test << foo;

if(test.str() == "2+7i")
  //... 

[tjlusco]

Thanks! I was unfamiliar with the use of stringstreams so I wasn't sure if they were compatible with normal i/ostream operators. So the compiler will automatically typecast a stringstream to the appropriate istream/ostream as necessary in the operators? Correct me if that is wrong.

[Disch]

stringstreams are both istreams and ostreams, so yes, it will work just fine with your operators.