How to write a python script that test my c++?

Question

Say I wanna test my c++ code but I don't want to do it by hand. I realize I can write a python script that can test my code for me. So I want to test this c++ code for example:

#include <iostream>
#include <string>
using namespace std;
int main() {
 string line;
 cin >> line;
 cout << line << endl;
}

Here is the python script that I tried to test this c++ code:

import subprocess as sb
sb.call("g++ main.cpp", shell=True)
sb.call("./a.out", shell=True)
sb.call("chocolate", shell=True)

This create the a.out executable file but it doesn't allow me to run my program. How can I make this work? Or is there something better that I can do?

• Mats Petersson: Removing "C++" tag, as your question is not about how to do something in C++, but how to do something in Python - even if you put some C++ code in the question, that is not the code you are asking about [directly].
• Mats Petersson: You could use subprocess.pipe and Popen.communicate, perhaps?
• Prune: Possible duplicate of Python executing shell command doesn't terminate
• Borys Serebrov: Why do you want to test your C++ code with python script? Is there any special reason for that? I think it is more natural and easier to use C++ unit testing libraries like boots.test.
• tdelaney: @BorisSerebrov We have an entire test team that writes tests for c++ programs in python. These tests drive the C++ at the command line level and by using a foreign function interface when appropriate. This is not C++ unit testing of course (we do that too) but it is a major component of testing. Putting "boost" and "easy" in the same sentence may also be violating natural law.

Answer 1

Testing can get complicated but as a minimum you can use the subprocess.Popen object to manage the input and output of the program. Here is a minimalist test suite

import subprocess as sb
import threading
def timeout():
 print('timeout')
 exit(3)
sb.check_call("g++ main.cpp", shell=True)
t = threading.Timer(10, timeout)
proc = sb.Popen("./a.out", shell=True, stdin=sb.PIPE, stdout=sb.PIPE,
 stderr=sb.PIPE)
out, err = proc.communicate('hello\n')
t.cancel()
assert proc.returncode == 0
assert out == 'hello\n'
assert err == ''
sb.check_call("chocolate", shell=True)