How to capture stdout/stderr with googletest?
I have used this snippet before to redirect cout calls to a stringstream when testing output. Hopefully it might spark some ideas. I've never used googletest before.
// This can be an ofstream as well or any other ostream
std::stringstream buffer;
// Save cout's buffer here
std::streambuf *sbuf = std::cout.rdbuf();
// Redirect cout to our stringstream buffer or any other ostream
std::cout.rdbuf(buffer.rdbuf());
// Use cout as usual
std::cout << "Hello World";
// When done redirect cout to its old self
std::cout.rdbuf(sbuf);
Before redirecting back to the original output use your google test to check the output in buffer.
Avoiding having to do this is always a good design idea. If you really want to do it the following works:
#include <cstdio>
#include <cassert>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <iostream>
int main() {
int fd = open("my_file.log", O_WRONLY|O_CREAT|O_TRUNC, 0660);
assert(fd >= 0);
int ret = dup2(fd, 1);
assert(ret >= 0);
printf("This is stdout now!\n");
std::cout << "This is C++ iostream cout now!" << std::endl;
close(fd);
}
To use stderr instead of stdout change the second argument to dup2 to be 2. For capturing without going via a file you could use a pipe pair instead.
Googletest offers functions for this:
testing::internal::CaptureStdout();
std::cout << "My test";
std::string output = testing::internal::GetCapturedStdout();